H2 Maths Distinction Rate (Percentage of As)

H2 Mathematics has one of the highest distinction rates of all subjects (around 50% each year). This means that around half of all Singaporean A level candidates score an A for H2 Maths!

H2 A Level Distinction Rates Compilation (National Average)

(For year 2010)

H2 Mathematics Distinction Rate:  51.9%
H2 Biology Distinction Rate: 43.7%
H2 Economics Distinction Rate: 33.8%

H1 Mathematics Distinction Rate: 33.1%
H1 Economics Distinction Rate: 33.8%

Literature Distinction Rate: 30.1%
History Distinction Rate: 23.7%
Geography Distinction Rate: 28.3%

Source: http://ajc.edu.sg/pdf/aj_broadcast/newsroom/news_archives/linkaj_may_2011.pdf


 H2 Maths Notes and Resources

Check out the highly summarized and condensed H2 Maths Notes here! (Comes with Free H2 Math Exam Papers.)


 Is H2 Maths the easiest H2 subject to get A?

Answer: Yes, provided the student does study conscientiously and not lag behind too much. Based on the statistics above, one can easily see that based on probability alone, H2 Maths is the easiest H2 subject to get A. Since more than 50% of students get A for H2 Maths, in a sense it is easier to get A for H2 Maths than flipping a heads on a coin!

However… (Please Read)

H2 Maths is also the easiest to fail! Without sufficient practice and effort to understand the subject material, sub-30 (below 30/100) marks are extremely common for H2 Maths. Last minute cramming will simply not work, and if a student lags too far behind in terms of syllabus, it will take extra effort to just even catch up.

In Depth Analysis of H2 Maths Distinction Rate

The 50% National Distinction Rate for H2 Maths can be quite misleading to think that every student has 50% chance of getting A for H2 Maths. The truth is that H2 Maths Distinction Rate varies a lot from school to school.

For example, AJC’s H2 Maths Distinction Rate is 62.7%, which is very much higher than the 50% average National Distinction Rate.

Raffles Institution (RI/RJC) Distinction Rate hovers around 70% to 80%!

Victoria JC (VJC)’s H2 Maths Distinction Rate is around 66.6%.

Hwa Chong (HCI) H2 Maths Distinction Rate is around 80% (8 out of 10 students scored an A for H2 Maths in HCI for three consecutive years).

Upon some thinking, one will quickly realize that if so many schools have Distinction Rate significantly above 50%, there has to be many schools with Distinction Rate significantly below 50%, in order for the National Distinction Rate to be around 50%!

The only people who know the exact Distinction Rate for the above mentioned JCs would be the internal staff and students, since the school website will probably not publish the statistics for obvious reasons.

The Best Time to Study H2 Maths is Now!

For students who are in schools with super high H2 Maths Distinction Rate, congratulations, your chances of getting A for H2 Maths are very good. However, do not be complacent till the very last day, as the race is not over yet.

For students who are in schools with very low H2 Maths Distinction Rate, the odds are unfortunately stacked against the student. However, do not lose heart, as anything is possible if one puts one’s heart and mind into it.

Good luck!


H2 Maths Notes and Resources

Check out the highly summarized and condensed H2 Maths Notes here! (Comes with Free H2 Math Exam Papers.)


H2 Math Tuition

https://mathtuition88.com/

The Brain of John Conway (Gifted Mathematician’s Brain)

The book mentioned in the video can be found here:

Genius At Play: The Curious Mind of John Horton Conway

Many scientists and research has revealed that the true source of genius comes from both nature and nurture.

Talent is Overrated: What Really Separates World-Class Performers from Everybody Else

GEP Test Dates (August)

In August, Primary 3 pupils in Singapore schools have the opportunity to take the GEP Screening Test, comprising 2 papers: English Language and Mathematics.

Check out the Recommended Books for GEP Test here!

IQ is based on both nature (inheritance of genes), and more importantly nurture (habits, family background, books read as a child, …), hence a logical way to prepare for the GEP is to read some books relevant to the GEP test. Some preparation is always better than zero preparation, as authors of many self-help books have researched and concluded.

It would be a huge advantage for students to be familiar with basic logic quizzes that are found in IQ tests. Seeing this type of question for the first time in the GEP test would not be very conducive as it may lead to nervousness which would affect the logical thinking.

circle-traingle-puzzle-iq-test
To do well in the time based GEP test, it would be a great advantage to have seen such questions before. (Found in the Recommended Books for GEP link above)

“I LOVE YOU” Math Graph

This is how to plot “I LOVE YOU” using Math Graphs (many piecewise functions plotted together).

Interesting? Share it using the buttons below this post!

Source: Found it on Weibo (China’s version of Facebook)

i love you graph


Love and Math: The Heart of Hidden Reality

What if you had to take an art class in which you were only taught how to paint a fence? What if you were never shown the paintings of van Gogh and Picasso, weren’t even told they existed? Alas, this is how math is taught, and so for most of us it becomes the intellectual equivalent of watching paint dry.

In Love and Math, renowned mathematician Edward Frenkel reveals a side of math we’ve never seen, suffused with all the beauty and elegance of a work of art. In this heartfelt and passionate book, Frenkel shows that mathematics, far from occupying a specialist niche, goes to the heart of all matter, uniting us across cultures, time, and space.

BMAT Book Recommendations for NTU Medicine

Recommended BMAT Books

#1 Recommended BMAT Book

How to Master the BMAT: Unbeatable Preparation for Success in the BioMedical Admissions Test

Thinking of applying to the new Medical School at NTU?

NTU’s application requires the BMAT (Biomedical Admissions Test). Applicants will have to register for the Biomedical Admissions Test (BMAT) and take the BMAT as part of the criteria for entry to the LKCMedicine MBBS programme.
Source: http://www.lkcmedicine.ntu.edu.sg/admissions/Pages/Entry-Requirements-And-Selection-Criteria.aspx

BMAT is useful for applying to Britain’s medical schools too.

NTU only takes in 50-150 students per year, out of Singapore’s entire population! Hence, one can imagine it is definitely not easy to get into NTU medicine.

How to get into NTU Medicine

According to this article by Straits Times, “the final 54 chosen medical students – all Singaporeans – had almost perfect scores in the interviews and also aced their BioMedical Admissions Test (BMAT).”

Getting 4 As is too extremely common in top JCs like RJC or HCI (pick any random guy from the top JCs and he/she is likely to have 4As), hence the distinguishing factor would be your BMAT score.

The BMAT is set by the British, and hence unlike anything students have seen in Singapore. In particular the format and style are different from the standard Singaporean style of testing.

Currently the acceptance rate for NTU medicine is 54/800 (6.75% acceptance rate), which means that getting into NTU medicine is as hard as getting into Ivy League Universities like Harvard / Princeton!!! (Harvard = 5.9% Acceptance Rate, Princeton = 7.4% Acceptance Rate)

Singaporeans are known to be extremely keen when it comes to studying Medicine / Law, and hence competition is definitely going to increase, and a good BMAT book will help you rise above the competition.

TOP BMAT Books in the Market

#1 Recommended BMAT Book

How to Master the BMAT: Unbeatable Preparation for Success in the BioMedical Admissions Test

#2 Recommended BMAT Book

The Ultimate BMAT Guide – 600 Practice Questions: Fully Worked Solutions, Time Saving Techniques, Score Boosting Strategies, 10 Annotated Essays, 2016 Entry Book (BioMedical Admissions Test)

#3 Recommended BMAT Book

Passing the UKCAT and BMAT: Advice, Guidance and Over 650 Questions for Revision and Practice (Student Guides to University Entrance Series)

#4 Recommended BMAT Book

How to Master the BMAT: Unbeatable Preparation for Success in the BioMedical Admissions Test

#5 Recommended BMAT Book

BMAT Secrets Study Guide: BMAT Exam Review for the BioMedical Admissions Test

NTU Medicine Interview (Does NTU Medicine need interview?)

Yes, NTU Medicine does have interview, in fact it has Eight Interviews.

Many top scorers (4As, perfect score, perfect portfolio) have unfortunately been weeded out at the interview if they are not adept at interviews or verbally expressing themselves. This is very unfortunate for those who have studied so hard, but yet got eliminated at the interview stage, and have to go to Australia to study Medicine (costs half a million SGD!!!) or even abandon their dream of being a doctor.

Fortunately, Medicine Interview is something that you can prepare for. Do be prepared for an answer to the question “Why do you want to study Medicine?”. The interviewers are looking for compassionate doctors, not money-minded individuals who want to fatten their bank account.

The interview would be a bit difficult for quiet / introverted people, which is a pity, since introverts can be very good doctors too. Interviews tend to favor extroverts, or those who are adept at self-promotion (do be humble though). Hence, if you are more of an introvert, you would need to work doubly hard to prepare for the interview.

Recommended Medicine Interview Books (Suitable for NTU / NUS Medicine Interview)

#1 Medicine Interview Book

Medicine Interview questions and answers with full explanations: The comprehensive guide to the medicine interview for 2013-2014 applicants

#2 Medicine Interview Book

Why Medicine?: And 500 Other Questions for the Medical School and Residency Interviews

#3 Medicine Interview Book

The Medical School Interview: Secrets and a System for Success

#4 Medicine Interview Book

The Medical School Interview: Winning Strategies from Admissions Faculty

#5 Medicine Interview Book

The Medical School Interview: From preparation to thank you notes: Empowering advice to help you succeed

Good luck and all the best!

Hunt for the Elusive 4th Klein Bottle – Numberphile

Look through this video to discover the 4 types of Klein Bottles!

Math Geek: From Klein Bottles to Chaos Theory, a Guide to the Nerdiest Math Facts, Theorems, and Equations

Where to Buy Klein Bottles

If you are fascinated by Klein Bottles, you can check out the website mentioned in the video: http://www.kleinbottle.com/

The website sells Klein Bottles under the name Acme Klein Bottles, made by Cliff Stohl.

Free Shipping+ have Back Lighting BESTA CD-580+ English Chinese Electronic Dictionary Translator

mathtuition88's avatarChinese Tuition Singapore

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Lemma on Measure of Increasing Sequences in X

(Continued from https://mathtuition88.com/2015/06/20/what-is-a-measure-measure-theory/)

Lemma: Let \mu be a measure defined on a \sigma-algebra X.

(a) If (E_n) is an increasing sequence in X, then

\mu (\bigcup_{n=1}^\infty E_n )=\lim \mu (E_n)

(b) If F_n) is a decreasing sequence in X and if \mu (F_1)<\infty, then

\mu (\bigcap_{n=1}^\infty F_n )=\lim \mu (F_n )

Note: An increasing sequence of sets (E_n) means that for all natural numbers n, E_n \subseteq E_{n+1}. A decreasing sequence means the opposite, i.e. E_n \supseteq E_{n+1}.

Proof: (Elaboration of the proof given in Bartle’s book)

(a) First we note that if \mu (E_n) = \infty for some n, then both sides of the equation are \infty, and inequality holds. Henceforth, we can just consider the case \mu (E_n)<\infty for all n.

Let A_1 = E_1 and A_n=E_n \setminus E_{n-1} for n>1. Then (A_n) is a disjoint sequence of sets in X such that

E_n=\bigcup_{j=1}^n A_j, \bigcup_{n=1}^\infty E_n = \bigcup_{n=1}^\infty A_n

Since \mu is countably additive,

\mu (\bigcap_{n=1}^\infty E_n) = \sum_{n=1}^\infty \mu (A_n) (since (A_n) is a disjoint sequence of sets)

=\lim_{m\to\infty} \sum_{n=1}^m \mu (A_n)

By an earlier lemma \mu (F\setminus E)=\mu (F)-\mu (E), we have that \mu (A_n)=\mu (E_n)-\mu (E_{n-1}) for n>1, so the finite series on the right side telescopes to become

\sum_{n=1}^m \mu (A_n)=\mu (E_m)

Thus, we indeed have proved (a).

For part (b),  let E_n=F_1 \setminus F_n, so that (E_n) is an increasing sequence of sets in X.

We can then apply the results of part (a).

\begin{aligned}    \mu (\bigcup_{n=1}^\infty E_n) &=\lim \mu (E_n)\\    &=\lim [\mu (F_1)-\mu (F_n)]\\    &=\mu (F_1) -\lim \mu (F_n)    \end{aligned}

Since we have \bigcup_{n=1}^\infty E_n =F_1 \setminus \bigcap_{n=1}^{\infty} F_n, it follows that

\mu (\bigcup_{n=1}^\infty E_n) =\mu (F_1)-\mu (\bigcap_{n=1}^\infty F_n)

Comparing the above two equations, we get our desired result, i.e. \mu (\bigcap_{n=1}^\infty F_n) = \lim \mu (F_n).

Reference:

The Elements of Integration and Lebesgue Measure

What does it mean to be smart in mathematics?

teachmathculture's avatarteaching/math/culture

In the last two posts, I discussed the idea of status. First, I talked about why status matters, then I talked about how teachers can see it in the classroom.

Sometimes, after I have explained how status plays out in the classroom, somebody will push back by saying, “Yeah, but status is going to happen. Some kids are just smarter than others.”

I am not naive: I do not believe that everybody is the same or has the same abilities. I do not even think this would be desirable. However, I do think that too many kids have gifts that are not recognized or valued in school — especially in mathematics class.

Let me elaborate. In schools, the most valued kind of mathematical competence is typically quick and accurate calculation. There is nothing wrong with being a fast and accurate calculator: a facility with numbers and algorithms no…

View original post 589 more words

The Groupoid Properties of Operation * on Path-homotopy Classes (Proof)

(Continued from https://mathtuition88.com/2015/06/18/the-groupoid-properties-of-on-path-homotopy-classes/)

Theorem: The operation * has the following properties:

(1) (Associativity) [f]*([g]*[h])=([f]*[g])*[h], i.e. it doesn’t matter where we place the brackets.

(2) (Right and left identities) Given x\in X, let e_x denote the constant path e_x: I\to X mpping all of I to the point x. If f is a path in X from x_0 to x_1, then [f]*[e_{x_1}]=[f] and [e_{x_0}]*[f]=[f].

(3) (Inverse) Given the path f in X from x_0 to x_1, let \bar{f} be the path defined by \bar{f}=f(1-s). \bar{f} is called the reverse of f. Then, [f]*[\bar{f}]=[e_{x_0}] and [\bar{f}]*[f]=[e_{x_1}].

We will prove the above statements, of which (1) Associativity is actually the trickiest.

Proof:

We shall prove two elementary lemmas first. (This part is not proved in the book by Munkres).

Lemma 1: If k: X\to Y is a continuous map, and if F is a path homotopy in X between the paths f and f’, then k\circ F is a path homotopy in Y between the paths k\circ f and k\circ f'.

Proof of Lemma 1: Since F is a path homotopy in X between paths f and f’, we have by definition that F(s,0)=f(s), F(s,1)=f'(s), F(0,t)=x_0, F(1,t)=x_1.

Then, k F(s,0)=kf(s), kF(s,1)=kf'(s), kF(0,t)=k(x_0), kF(1,t)=k(x_1). Since kF is continuous (composition of two continuous functions), kF is inded a path homotopy in Y between he paths kf and kf’.

Lemma 2: If k:X\to Y is a continuous map and if f and g are paths in X with f(1)=g(0), then

k\circ (f*g)=(k\circ f)*(k \circ g)

Proof of Lemma 2:

k(f*g)(s)=kh(s), where h=f*g as defined previously.

(kf)*(kg)(s)=kh(s).

We will first verify property (2) on Right and Left Identities. Let e_{x_0} denote the constant path in I at 0, and we let i: I\to I denote the identity map, which is a path in I from 0 to 1. Then e_0 * i is also a path in I from 0 to 1.

Because I is convex, there is a path homotopy G in I between i and e_0 *i (Straight-line homotopy) Then f\circ G is a path homotopy in X between the paths f\circ i=f and f\circ (e_0 *i) (Lemma 1). Furthermore by Lemma 2, f\circ (e_0 *i) = (f \circ e_0) * (f \circ i) which is equivalent to e_{x_0} *f.

A similar argument, using the fact that if e_1 denotes the constant path at 1, then i*e_i is path homotopic in I to the path i, shows that [f]*[e_{x_1}]=[f].

To prove (3) (Inverse), we note that the reverse of i is \bar{i}(s)=1-s. Then i*\bar{i} is a path in I beginning and ending at 0. The constant path e_0 is also beginning and ending at 0. Again, because I is convex, there is a path homotopy H in I between e_0 and i*\bar{i} (straight-line homotopy). Then, using lemma 1 and 2, f\circ H is path homotopy between f\circ e_0=e_{x_0} and f\circ (i*\bar{i})=(f\circ i)*(f\circ\bar{i})=f*\bar{f}. Very similarly, we can use the fact that \bar{i}*i is path homotopic  in I to e_1 to show that [\bar{f}]*[f]=[e_{x_1}].

We will continue the proof of associativity (which is longer) in the next blog post.

Source: Topology (2nd Economy Edition)

Recommended Maths Olympiad Books for Self Learning / Domain Test

I have added more Math Olympiad books suitable for students training for GEP Math / DSA Math.
These are books actually bought by a viewer of my website through my Amazon affiliate link.
Just to share, and hope it is helpful!

mathtuition88's avatarMathtuition88

A First Step to Mathematical Olympiad Problems (Mathematical Olympiad Series)The Art of Problem Solving, Vol. 1: The Basics

The first book is written by Professor Derek Holton. Prof Holton writes a nice column for a Math magazine, which gives out books as prizes to correct solutions. I tried some of the problems here: Maths Olympiad Magazine Problems.

GEP Math Olympiad Books

If you are searching for GEP Math Olympiad Books to prepare for the GEP Selection Test, you may search for Math Olympiad Books for Elementary School. Note that Math Olympiad Books for IMO (International Mathematics Olympiad) are too difficult even for a gifted 9 year old kid!

A suitable book would be The Original Collection of Math Contest Problems: Elementary and Middle School Math Contest problems. It covers the areas of Algebra, Geometry, Counting and Probability, and Number Sense, over 500 examples and problems with fully explained solutions.

View original post 98 more words

Qoo10 (Singapore’s Cheapest Online Shopping Mall)

Just to share with my Singaporean readers on 5 ways to save money while shopping!

1) Universal Studios Ticket

This is a very good bargain, Qoo10 is selling the Universal Studios Singapore Ticket at half the retail price. Normal price is $74. If you haven’t visited USS yet, this June holidays is a good time.

[S$35.99][Holiday Special]Universal Studio Singapore Ticket USS One day Pass 新加坡环球影城 / Christmas Celebration.Best Price Guaranteed! / RESORTS WORLD SENTOSA

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2) Cheap and good iPhone Cable

Everyone knows that the official Apple cable is very expensive, overpriced in fact. Most people just need a basic iPhone cable that can charge and connect to computer. I personally bought this cable, at $3.70 it is extreme value for money. So far so good, it charges and transfer data well.  I don’t think you can find another place with such low price for a cable.

[S$3.70]Aluminum Steel Wire mesh/Nylon Fabric Lightning cable for iPhone6/6 Plus/5/5S/5C/iPad 4/iPad Air/iPad Mini/Mini2(Support IOS8)

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3) Amazon Kindle

At $99, it is one of the cheapest electronic items out there (as compared to iPhone, iPad, etc.) Also, Kindle is ideal as a gift to students as it is very education oriented, and has less games than the iPad (a upside for children).

[S$99.00][Kindle]★Amazon Kindle 2015 with Free eBooks! (2015 KINDLE 7th Gen/ Kindle Paperwhite 2015)- 7000 eBooks Free with Cover or Slip Case Purchased! Best Amazon Kindle Paperwhite Voyage Reader Tablet! ★

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4) Cheapest Computer in Singapore

This notebook (from HP) would be a good choice if you need a basic laptop for school work. There are other brands (Asus, Lenovo) at similar prices at Qoo10. Very few physical shops have computers at this price.

[S$299.00][HP]*** GSS Special Price *** HP 250 14inch Dual Core Notebook / Intel N2840 Processor / 2GB Ram / 500GB HDD / Windows 8.1 / Intel HD Graphics / Only 1.9Kg / 1 Year Limited International HP Warranty

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5) Cat6 Ethernet Cable

Many households (including myself, until recently) are still using Cat5 / Cat5e old cables which would impact your internet speed. No point subscribing to the best internet plan, and have it all slowed down by an outdated Cat5 cable. This Cat6 Ethernet Cable may be what you need to boost your internet connection.

[S$3.90]Cat6 Ethernet Network Patch Cable – UTP BCC Stranded FLUKE® Tested | 0.5m to 3m | UTP BCC | Blue

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What is a Measure? (Measure Theory)

In layman’s terms, “measures” are functions that are intended to represent ideas of length, area, mass, etc. The inputs for the measure functions would be sets, and the output would be a real value, possibly including infinity.

It would be desirable to attach the value 0 to the empty set \emptyset and measures should be additive over disjoint sets in X.

Definition (from Bartle): A measure is an extended real-valued function \mu defined on a \sigma-algebra X of subsets of X such that
(i) \mu (\emptyset)=0
(ii) \mu (E) \geq 0 for all E\in \mathbf{X}
(iii) \mu is countably additive in the sense that if (E_n) is any disjoint sequence (E_n \cap E_m =\emptyset\ \text{if }n\neq m) of sets in X, then

\displaystyle \mu(\bigcup_{n=1}^\infty E_n )=\sum_{n=1}^\infty \mu (E_n).

If a measure does not take on +\infty, we say it is finite. More generally,  if there exists a sequence (E_n) of sets in X with X=\cup E_n and such that \mu (E_n) <+\infty for all n, then we say that \mu is \sigma-finite. We see that if a measure is finite implies it is \sigma-finite, but not necessarily the other way around.

Examples of measures

(a) Let X be any nonempty set and let X be the \sigma-algebra of all subsets of X. Let \mu_1 be definied on X by \mu_1 (E)=0, for all E\in\mathbf{X}. We can see that \mu_1 is finite and thus also \sigma-finite.

Let \mu_2 be defined by \mu_2 (\emptyset) =0, \mu_2 (E)=+\infty if E\neq \emptyset. \mu_2 is an example of a measure that is neither finite nor \sigma-finite.

The most famous measure is definitely the Lebesgue measure. If X=R, and X=B, the Borel algebra, then (shown in Bartle’s Chapter 9) there exists a unique measure \lambda defined on B which coincides with length on open intervals. I.e. if E is the nonempty interval (a,b), then \lambda (E)=b-a. This measure is usually called Lebesgue measure (or sometimes Borel measure). It is not a finite measure since \lambda (\mathbb{R})=\infty. But it is \sigma-finite since any interval can be broken down into a sequence of sets (E_n) such that \mu (E_n)<\infty for all n.

Source: The Elements of Integration and Lebesgue Measure

Primary One registration for 2016 to open on July 2

Source: http://www.todayonline.com/singapore/primary-one-registration-2016-open-july-2

SINGAPORE — The Primary One registration exercise for next year’s intake will open from July 2 to Aug 27, the Ministry of Education (MOE) said today (June 18).

Three new schools — Oasis Primary, Punggol Cove Primary and Waterway Primary — will be open for P1 registration and will be taking in students from next year.

“The cohort size for 2016 is similar to that of 2015. There will be sufficient school places for all eligible P1 students on a regional and nationwide basis,” said the MOE.

More information on the list of primary schools and vacancies available as well as a list of registration centres for new schools can be found on the P1 registration website at http://www.moe.gov.sg/education/admissions/primary-one-registration/

Prepare Early Beforehand for GEP / DSA / PSLE

Join the Kiasuparents 2020 PSLE Discussion Group

This is the ultimate uniquely Singapore “Kiasuparents” 2020 PSLE Discussion Group: http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=81381


The Smartest Kids in the World: And How They Got That Way

This book is the #1 Best Seller on Amazon (in the Gifted Education section)! Learn about the secret of the smartest kids in the world, and how you can be one of them.

The Groupoid Properties of * on Path-homotopy Classes

This is one of the first instances where algebra starts to appear in Topology. We will continue our discussion of material found in Topology (2nd Economy Edition) by James R. Munkres.

First, we need to define the binary operation *, that will later make * satisfy properties that are very similar to axioms for a group.

Definition: If f is a path in X from x_0 to x_1, and if g is a path in X from x_1 to x_2, we define the product f*g of f and g to be he path h given by the equations

h(s)=\begin{cases}f(2s) &\text{for }s\in [0,\frac{1}{2}], \\ g(2s-1)& \text{for }s\in[\frac{1}{2}, 1]\end{cases}

Well-defined: The function h is well-defined, at s=1/2, f(1)=x_1, g(0)=x_1.

Continuity: h is also continuous by the pasting lemma.

h is a path in X from x_0 to x_2. We think of h as the path whose first half is the path f and whose second half is the path g.

We will verify that the product operation on paths induces a well-defined operation on path-homotopy classes, defined by the equation [f]*[g]=[f*g]

Let F be a path homotopy between f and f’, and let G be a path homotopy between g and g’.

i.e. we have F(s,0)=f(s), F(s,1)=f'(s)
F(0,t)=x_0, F(1,t)=x_1
G(s,0)=g(s), G(s,1)=g'(s)
G(0,t)=x_1, G(1,t)=x_2

We can define:

H(s,t)=\begin{cases}F(2s,t) &\text{for }s\in[0,\frac{1}{2}],\\ G(2s-1,t)&\text{for }s\in[\frac{1}{2},1]\end{cases}.

We can check that F(1,t)=x_1=G(0,t) for all t, hence the map H is well-defined. H is continuous by the pasting lemma.

Let’s check that H is the required path homotopy between f*g and f’*g’.

For s in [0,1/2],

H(s,0) = F(2s,0) =f(2s)=h(s)

H(s,1) = F(2s,1) =f'(2s)=h'(s)
h’ := f’ * g’

H(0,t) = F(0,t) = x_0

s in [1/2,1] works fine too:

H(s,0) = G(2s-1,0) = g(2s-1)=h(s)

H(s,1) = G(2s-1,1)= g'(2s-1) = h'(s)

H(1,t) = G(1,t)= x_2

Thus, H is indeed the required path homotopy between f*g and f’*g’. * is almost like a binary operation for a group. The only difference is that [f]*[g] is not defined for every pair of classes, but only for those pairs [f], [g] for which f(1) = g(0), i.e. the end point of f is the starting point of g.

Functions between Measurable Spaces

Sometimes, it is  desirable to define measurability for a function f from one measurable space (X,X) into another measurable space (Y,Y). In this case one can define f to be measurable if and only if the set f^{-1} (E)=\{x\in X: f(x) \in E\} belongs to X for every set E belonging to Y.

This definition of measurability appears to differ from Definition 2.3 (earlier in the book), but Definition 2.3 is in fact equivalent to this definition in the case that Y=R and Y=B.

First, lets recap what is Definition 2.3:

A function f on X to R is said to be X-measurable (or simply measurable) if for every real number \alpha the set \{x\in X:f(x)>\alpha\} belongs to X.

Let (X,X) be a measurable space and f be a real-valued function defined on X. Then f is X-measurable if and only if f^{-1 }(E)\in X for every Borel set E.

Thus there is a close analogy between the measurable functions on a measurable space and continuous functions on a topological space.

Source:

The Elements of Integration and Lebesgue Measure

Homotopy of Paths

For this post we will explain what is a homotopy of paths.

Source: Topology (2nd Economy Edition)

The book above is a nice introductory book on Topology, which includes a section of introductory Algebraic Topology.

Definition: If f and f’ are continuous maps of the space X into the space Y, we say that f is homotopic to f’ if there is a continuous F: X x I -> Y such that

F(x, 0)=f(x) and F(x,1) = f'(x)

for each x. The map F is called a homotopy between f and f’. If f is homotopic to f’, we write f \simeq f'.

If f and f’ are two paths in X, there is a stronger relation, called path homotopy, which requires that the end points of the path remain fixed during the deformation. We write f \simeq_p f' if f and f’ are path homotopic.

Next, we will prove that the relations \simeq and \simeq_p are equivalence relations.

If f is a path, we shall denote its path-homotopy equivalence class by [f].

Proof: We shall verify the properties of an equivalence relation, namely reflexivity, symmetry and transitivity.

Reflexivity:

Given f, it is rather easy to see that f \simeq f. The map F(x,t) is the required homotopy.

F(x,0)=f(x) and F(x,1)=f(x) is clearly satisfied.

If f is a path, then F is certainly a path homotopy, since f and f itself has the same initial point and final point.

Symmetry:

Next we shall show that given f \simeq f', we have f' \simeq f. Let F be a homotopy between f and f’. We can then verify that G(x,t) = F(x, 1-t) is a homotopy between f’ and f.

G(x,0) = F(x, 1)=f’ (x)

G(x,1) = F(x, 0) = f(x)

Furthermore, if F is a path homotopy, so is G.

G(0,t)=F(0, 1-t) = x_0

G(1,t)=F(1,1-t) = x_1

Transitivity:

Next, suppose that f \simeq f' and f' \simeq f'', we show that f \simeq f''. Let F be a homotopy between f and f’, and let F’ be a homotopy between f’ and f”. This time, we need to define a slightly more complicated homotopy G: X x I -> Y by the equation

G(x,t) = \begin{cases} F(x,2t) &\text{for }t\in [0,\frac{1}{2}],\\ F'(x, 2t-1) &\text{for } t\in [\frac{1}{2}, 1].\end{cases}

First, we need to check if the map G is well defined at t=1/2. When t=1/2, we have F(x,2t) = F(x,1)=f'(x) = F'(x,2t-1).

Because G is continuous on the two closed subsets X x [0, 1/2] and X x [1/2, 1] of XxI, it is continuous on all of X x I, by the pasting lemma.

Thus, we may see that G is the required homotopy between f and f”.

G(x,0)=F(x,0) = f(x)

G(x,1) = F’ (x, 1) = f”(x)

We can also check that if F and F’ are path homotopies, so is G.

G(0,t) = F(0, 2t) = x_0

G(1, t)=F'(1, 2t-1) = x_1

A math question has been stumping thousands of British students

Many people have the notion that UK British GCSE is very easy, but there seems to be a very tough Probability question that has appeared!

Here’s the question on the test, which was set by the British education and examination board Edexcel

There are n sweets in a bag. Six of the sweets are orange. The rest of the sweets are yellow. Hannah takes a random sweet from the bag. She eats the sweet. Hannah then takes at random another sweet from the bag. She eats the sweet. The probability that Hannah eats two orange sweets is 1/3. Show that n²-n-90=0.

Source: http://mashable.com/2015/06/05/math-exam-gcse-question/

This is really one tough question for 15, 16 year old kids.

Do try it out, and if you are stuck you can check out the solution by Professor Ian Dryden, the head of mathematical sciences at the University of Nottingham, at the link above.

Probability Demystified 2/E

Check out this book to get enlightened on the mysterious topic of probability.

Real Life Applications of Algebraic Topology (Big Data)

Big Data: A Revolution That Will Transform How We Live, Work, and Think

What is Algebraic Topology:

Algebraic topology is a branch of mathematics that uses tools from abstract algebra to study topological spaces. The basic goal is to find algebraic invariants that classify topological spaces up to homeomorphism, though usually most classify up to homotopy equivalence. (Wikpedia)

What is Big Data:

Big data is a broad term for data sets so large or complex that traditional data processing applications are inadequate. Challenges include analysis, capture, data curation, search, sharing, storage, transfer, visualization, and information privacy. The term often refers simply to the use of predictive analytics or other certain advanced methods to extract value from data, and seldom to a particular size of data set. Accuracy in big data may lead to more confident decision making. And better decisions can mean greater operational efficiency, cost reductions and reduced risk. (Wikipedia)


Big Data is said to be the next biggest scientific advance since the internet. Algebraic Topology is one branch of Mathematics that is directly related to Big Data.

Topological data analysis (TDA) is a new area of study aimed at having applications in areas such as data mining and computer vision. The main problems are:

  1. how one infers high-dimensional structure from low-dimensional representations; and
  2. how one assembles discrete points into global structure.

The human brain can easily extract global structure from representations in a strictly lower dimension, e.g. we infer a 3D environment from a 2D image from each eye. The inference of global structure also occurs when converting discrete data into continuous images, e.g. dot-matrix printers and televisions communicate images via arrays of discrete points.

The main method used by topological data analysis is:

  1. Replace a set of data points with a family of simplicial complexes, indexed by a proximity parameter.
  2. Analyse these topological complexes via algebraic topology — specifically, via the theory of persistent homology.[1]
  3. Encode the persistent homology of a data set in the form of a parameterized version of a Betti number which is called a persistence diagram or barcode.[1]

Source: Wikipedia

 

Very interesting!

A nonnegative function f in M(X,X) is the limit of a monotone increasing sequence in M(X,X)

We will elaborate on a lemma in the book The Elements of Integration and Lebesgue Measure.

Lemma: If f is a nonnegative function in M(X,X), then there exists a sequence (\phi_n) in M(X,X) such that:

(a) 0\leq \phi_n (x) \leq \phi_{n+1} (x) for x\in X, n\in\mathbb{N}.

(b) f(x) =\lim \phi_n (x) for each x\in X.

(c) Each \phi_n has only a finite number of real values.

Proof:

Let n be a fixed natural number. If k=0, 1, 2, …, n 2^n -1, let E_{kn} be the set

E_{kn}=\{ x\in X: k2^{-n} \leq f(x)<(k+1)2^{-n}\}.

If k=n2^n, let E_{kn}=\{x\in X: f(x) \geq n\}.

We note that the sets \{E_{kn}: k=0, 1,\ldots, n2^n\} are disjoint.

The sets also belong to X, and have union equal to X.

Thus, if we define \phi_n= k2^{-n} on E_{kn}, then \phi_n belongs to M(X,X).

We can see that the properties (a), (b), (c) hold.

(a): 0\leq k2^{-n}\leq k2^{-n-1} is true.

(I just noticed there is some typo in Bartle’s book, as the above inequality does not hold. I think n is supposed to be fixed, while k is increased instead.)

(b): As n tends to infinity, on k2^{-n} \leq f(x) <(k+1)2^{-n}, i.e. \phi_n (x) \leq f(x) < \phi_n (x)+2^{-n}, thus f(x)=\lim \phi_n (x) for each x\in X.

(c): Clearly true!

Source:

See also: Recommended Undergraduate Books

Error-Detecting and Error-Correcting Codes

Today’s post is a bit about coding theory, and how a good code can detect and even correct errors from transmission.

Theorem 1

A code is k-error-detecting if and only if the minimum Hamming distance between code words is at least k+1.

Theorem 2

A code is k-error-correcting if and only if the minimum Hamming distance between code words is at least 2k+1.

Hamming distance is the number of bits in which the code words differ. For instance, the Hamming distance between 1000 and 1001 is 1 since they only defer in the last bit.

Proof of Theorem 1

Lets assume a code is k-error-detecting. Suppose to the contrary the there is a pair of code words c_1 and c_2 with Hamming distance k or less. Then, given the code word c_2, we don’t know if it is a valid code word, or it arose from c_1 due to errors in k-bits. This contradicts the fact that the code is k-error-detecting.

If the minimum Hamming distance is at least k+1, then given a code that differs from a code word by k bits, we know that it is not a valid code word, and hence we have detected a error!

Proof of Theorem 2

Assume the code is k-error-correcting. Suppose to the contrary there is a pair of code words c_1 and c_2 whose Hamming distance is 2k or less. Then if there is a code word whose Hamming distance is k from c_1 and c_2, then it is equally likely to have arose from c_1 or c_2, hence we can’t correct the error!

If the Hamming distance is 2k+1 or more, then any code word with Hamming distance of k (or less) will be closer to one of the code words, and hence has higher probability of having arose from that code word.


The Imitation Game

During the winter of 1952, British authorities entered the home of mathematician, cryptanalyst and war hero Alan Turing (Benedict Cumberbatch) to investigate a reported burglary. They instead ended up arresting Turing himself on charges of ‘gross indecency’, an accusation that would lead to his devastating conviction for the criminal offense of homosexuality – little did officials know, they were actually incriminating the pioneer of modern-day computing. Famously leading a motley group of scholars, linguists, chess champions and intelligence officers, he was credited with cracking the so-called unbreakable codes of Germany’s World War II Enigma machine. An intense and haunting portrayal of a brilliant, complicated man, The Imitation Game a genius who under nail-biting pressure helped to shorten the war and, in turn, save thousands of lives.

Measurability of product fg

In the previous chapters, Bartle showed that that if f is in M(X,X), then the functions cf, f^2, |f|, f^+, f^- are also in M(X,X).

The case of the measurability of the product fg when f, g belong to M(X,X) is a little bit more tricky. If n\in\mathbb{N}, let f_n be the “truncation of f” defined by f_n (x)=\begin{cases}f(x), &\text{if }|f(x)|\leq n, \\ n, &\text{if } f(x)>n,\\ -n, &\text{if }f(x)<-n\end{cases}

Let g_m be defined similarly. We will work out the proof that f_n and g_m are measurable (Bartle left it as Exercise 2.K).

Proof:

Each f_n is a function on X to \mathbb{R}.

\{x\in X:f_n (x) >\alpha\}=\begin{cases}\{x \in X: f(x)>\alpha\}, &\text{if }-n<\alpha <n,\\ \emptyset, &\text{if }\alpha\geq n,\\X, &\text{if }\alpha\leq -n \end{cases}

All of the above sets are in X.

Thus, we may use an earlier Lemma 2.6 to show that the product f_n g_m is measurable.

We also have f(x)g_m (x)=\lim_n f_n (x)g_m (x), and using an earlier corollary that says that if a sequence (f_n) is in M(X,X) converges to f on X, then f is also in M(X,X), we have that f(x)g_m (x) belongs to M(X,X).

Finally, (fg)(x)=f(x)g(x)=\lim_m f(x)g_m (x), and hence fg also belongs to M(X,X).

This is a very powerful result of Lebesgue integration, since we can see that the theory includes extended real-valued functions, and prepares us to integrate functions that can reach infinite values!

Source: The Elements of Integration and Lebesgue Measure

Borel Measurable

This is a continuation of the study of the book The Elements of Integration and Lebesgue Measure by Bartle, listing a few examples of functions that are measurable. Bartle is a very good author, he tries his very best to make this difficult subject accessible to undergraduates.

Example:

If X is the set R of real numbers, and X is the Borel algebra B, then any monotone function is Borel measurable.

Proof:

Suppose that f is monotone increasing, i.e. x\leq x' implies f(x)\leq f(x').

Then, \{x\in\mathbb{R}:f(x)>\alpha\} consists of a half-line which is either of the form \{x\in\mathbb{R}:x>a\} or the form \{x\in\mathbb{R}:x\geq a\}. (We will show later that both cases can occur.) Thus,  the set will belong to the Borel algebra B which is the \sigma-algebra generated by all open intervals (a,b) in R.

Both cases can indeed occur. For example, if f(x)=x, then the set will be of the form \{x\in\mathbb{R}:x>a\}. More interestingly, if the set is the step function f(x)=\begin{cases}-1, &\text{if }x<0\\1, &\text{if }x\geq 0\end{cases}, then when \alpha=0, the set will be \{x\in\mathbb{R}:x\geq 0\}.


Lemma: An extended real-valued function f is measurable if and only if the sets A=\{x\in X:f(x)=+\infty\}, B=\{x\in X:f(x)=-\infty\} belong to X and the real-valued function f_1 defined by f_1 (x)= \begin{cases} f(x), &\text{if }x\notin A\cup B,\\ 0, &\text{if }x\in A\cup B,\end{cases} is measurable.

This lemma is often useful when dealing with extended real-valued functions.

Proof: If f is in M(X,X), it is proven earlier in the book by Bartle that A and B belong to X. Let \alpha\in\mathbb{R} and \alpha\geq 0, then we have that \{ x\in X:f_1 (x)>\alpha\}=\{ x\in X:f(x)>\alpha\}\setminus A which is in X since it is the complement of the union of A and X\setminus \{x\in X:f(x)>\alpha\}.

If \alpha<0, then \{ x\in X:f_1 (x)>\alpha \}=\{ x\in X:f(x)>\alpha \}\cup B, which is a union of two sets in X and hence also in X.

Hence, f_1 is measurable.

Conversely, if A, B\in \mathbf{X} and f_1 is measurable, then \{x\in X:f(x)>\alpha\}=\{ x\in X: f_1 (x) >\alpha \}\cup A when \alpha \geq 0, and \{x\in X:f(x)>\alpha\}=\{x \in X:f_1 (x)>\alpha\}\setminus B when \alpha <0, due to a similar reason as above. Therefore f is measurable!

Definitions for measurable functions

I am currently proceeding on a self-guided study of the book The Elements of Integration and Lebesgue Measure, will post some updates and elaborations of the proofs in the book. Every book is constrained by the number of pages the publisher allows, hence some authors will write rather terse and concise proofs, the worst example of which is simply “Proof: Trivial”. Bartle is a very good author, he does provide details of proofs 90% of the time.

Definition: A function f on X to R is said to be X-measurable (or simply measurable) if for every real number \alpha the set \{x\in X: f(x)>\alpha\} belongs to X.

This definition of measurability is not unique, there are other possible forms which are discussed in the lemma below.

Lemma: The following statements are equivalent for a function f on X to R:

((X,X) is a measurable space where X is a set and X is a \sigma-algebra of subsets of X.)

(a) For every \alpha\in\mathbb{R}, the set A_\alpha = \{x\in X: f(x)>\alpha \} belongs to X,

(b) For every \alpha\in\mathbb{R}, the set B_\alpha = \{x\in X: f(x)\leq\alpha \} belongs to X,

(c) For every \alpha\in\mathbb{R}, the set C_\alpha = \{x\in X: f(x)\geq\alpha \} belongs to X,

(d) For every \alpha\in\mathbb{R}, the set D_\alpha = \{x\in X: f(x)<\alpha \} belongs to X,

Proof:

Note that B_\alpha and A_\alpha are complements of each other, hence statement (a) is equivalent to statement (b). This is due to one of the properties of \sigma-algebra, namely that if A belongs to X, then the complement X\A also belongs to X.

Similarly, statements (c) and (d) are equivalent. We will prove that (a) is equivalent to (c).

Assume (a) holds, we can say that A_{\alpha-1/n} belongs to X for each n.

And since C_\alpha=\cap_{n=1}^{\infty}{A_{\alpha-1/n}}, it follows that C_\alpha\in\mathbf{ X}. Thus, (a) implies (c).

We also have A_\alpha =\cup_{n=1}^{\infty} C_{\alpha+1/n}, and hence if (c) is true, each C_{\alpha +1/n} is in X, and the union of them is also in X (definition for \sigma-algebra). It thus follows that (c) implies (a).

What this lemma says is that there is nothing special about the “>” in the definition of measurability. It could very well have been “\leq, or even “<” and nothing would change!

‘Beautiful Mind’ mathematician John Nash killed in US car crash

Very sad news…. Rest in peace, Professor John Nash.

Source: https://sg.news.yahoo.com/beautiful-mind-mathematician-john-nash-killed-us-police-143603056.html

Nobel Prize-winning US mathematician John Nash, who inspired the film “A Beautiful Mind,” was killed with his wife in a New Jersey car crash.

Nash, 86, and his 82-year-old wife Alicia were riding in a taxi on Saturday when the accident took place, State Police Sergeant Gregory Williams told AFP.

“The taxi passengers were ejected,” Williams said, adding that they were both killed.

The Princeton University and Massachusetts Institute of Technology (MIT) mathematician is best known for his contribution to game theory — the study of decision-making — which won him the Nobel economics prize in 1994.

His life story formed the basis of the Oscar-winning 2001 film “A Beautiful Mind” in which actor Russell Crowe played the genius, who struggled with mental illness.

“Stunned… my heart goes out to John & Alicia & family. An amazing partnership. Beautiful minds, beautiful hearts,” Crowe said on Twitter.

A Beautiful Mind

Synopsis: “HOW COULD YOU, A MATHEMATICIAN, BELIEVE THAT EXTRATERRESTRIALS WERE SENDING YOU MESSAGES?” the visitor from Harvard asked the West Virginian with the movie-star looks and Olympian manner. “Because the ideas I had about supernatural beings came to me the same way my mathematical ideas did,” came the answer. “So I took them seriously.”

Thus begins the true story of John Nash, the mathematical genius who was a legend by age thirty when he slipped into madness, and who—thanks to the selflessness of a beautiful woman and the loyalty of the mathematics community—emerged after decades of ghostlike existence to win a Nobel Prize for triggering the game theory revolution. The inspiration for an Academy Award–winning movie, Sylvia Nasar’s now-classic biography is a drama about the mystery of the human mind, triumph over adversity, and the healing power of love.

Measure and Integration Recommended Book

I have added a new addition to the Recommended Books for Undergraduate Math, which is one of my most popular posts!

The new book is The Elements of Integration and Lebesgue Measure, an advanced text on the theory of integration. At the high school level, students are exposed to integration, but merely the rules of integration. At university, students learn the Riemann theory of integration (Riemann sums), which is a good theory, but not the best. There are some functions which we would like to integrate, but do not fit nicely into the theory of Riemann Integration.

I am personally reading this book as well, as I didn’t manage to study it in university, but it is a key component for graduate level analysis. Students interested in advanced Probability (see this post on Coursera Probability course) would be needing Lebesgue theory too!

 

Time Management Tips for Students (What to do if fail JC Test / Promo Exam?)

Do you wish there is a method to improve your grades? How do you improve your grades after failing a Common Test for Secondary School or JC?

The Four Quadrant Method is an ideal method for students (especially higher level students like O Level or A Level students) to plan their study schedule and revision time table.

Many students do ok in primary school, but start to falter and fail in secondary school or JC. This may be due to many factors, some of which can be remedied using effective time management.

According to this model, which comes from the book First Things First by Stephen Covey (Highly recommended to read), there are four types of activities:

Quadrant 1) Important and Urgent (crises, deadline-driven projects)
Quadrant 2) Important, Not Urgent (preparation, prevention, planning, relationships)
Quadrant 3) Urgent, Not Important (interruptions, many pressing matters)
Quadrant 4) Not Urgent, Not Important (trivia, time wasters)

The key to doing well in school and exams is actually Quadrant 2! It is highly related to human psychology. Most people would think Quadrant 1 is more important, but actually Quadrant 2 is the most important type of activity for students.

Quadrant 1 activities (in the Singapore context) are activities like assignment due next day, test next day, exam the next day, and so on. They are important and also urgent. The thing is, these things are usually done by most people since there is a time pressure factor to it. Most students will actually do and complete Quadrant 1 activities. However, as you would know by now, just doing the homework the teacher assigns is not enough to do well for the test / exam under the Singapore syllabus. Firstly, the work that the teacher assigns may be basic material, while in Singapore, the school tests and exams all contain advanced and challenging material.

Quadrant 2 activities are long-ranged planning and strategies, like preparing for a test that is 3 months later, preparing for the Promo Exam that is half a year later. Since these activities are not urgent, most people skip them altogether. However, it is highly important to do Quadrant 2 activities everyday. Stephen R. Covey is a genius for discovering that Quadrant 2 is the secret to time management. Students should set aside some time everyday to do long-ranged preparation, e.g. preparing for a test that is a few months into the future.

Quadrant 3 activities are things that are urgent but not important. Examples are checking Email, checking Whatsapp for class group notifications. Yes, checking email and Whatsapp is compulsory nowadays, but it is not considered an important activity in the grand scheme of things. One should set a minimum amount of them for these activities. CCA may also be classified under this category. This Quadrant is highly deceptive, and a huge time sink, but in the end the activities in Quadrant 3 rank very low in importance.

Quadrant 4 activities are things that are not urgent and not important. Examples are checking Facebook, playing computer games, and so on. These activities should be kept to a bare minimum, and only during scheduled breaks for destressing.

The Four Quadrant technique can be coupled with the Pomodoro Technique which is another good technique for time management.

Hope it helps! This method is for parents to teach their child about Time Management, provided their child is motivated and wishes to improve. For children that are not motivated to study / not interested in learning, parents should check out these Motivational books to motivate students instead.

5-21-1471

Albrecht Durer, the German painter and engraver who studied mathematics and applied it to his art, was born in Nuremberg on this day.

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5-21-1923

Armand Borel born in Switzerland. He worked on Lie groups, algebraic groups, and arithmetic groups, helping transform many areas of mathematics, including algebraic topology, differential geometry, algebraic geometry, and number theory.

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Armand Borel

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5-21-1953

Set theorist Ernst Zermelo died in Freiburg, Germany. He worked on statistical mechanics and the calculus of variations until becoming intrigued by Cantor’s Continuum Hypothesis, posed as Hilbert’s First Problem in 1900, and switching to set theory.

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Tuition Agency / Chinese Tuition

Recommended Tuition Agency:

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There are many excellent tutors from RI, Hwa Chong, etc. at Startutor, teaching various subjects at all levels.
High calibre scholars from NUS/overseas universities are also tutoring at Startutor.

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让孩子读书更厉害的书籍

现在的家长都很注重孩子的学习,但是有时候孩子不专注,或者对学习没兴趣怎么办?

俗话说:你可以把马牵到水边,但你无法强迫它饮水(意指有的事情必需本人自愿,强迫无济于事);老牛不喝水,不能强按头。

可见,强逼孩子读书是没有用的,反而会造成孩子厌倦学习。最重要是培养孩子读书的兴趣,这样往往事半功倍,孩子的学习成绩突飞猛进。

在此,让我介绍一些帮忙孩子读书厉害的书:

1) 我的第一本专注力训练书(专注的孩子更聪明)

focus

现在很多孩子都有多动症,就算没有多动症也很难静下来读书,这是21世纪普遍的问题。因为现在太多引诱,比如电脑,手机,电视。毋庸置疑,专注的孩子更聪明,学习也肯定比较好。《我的第一本专注力训练书 》为《看到找不到》系列之精彩合集。精选本系列中最经典和最受欢迎的形象页面,按综合难度由易到难编排,增加了专注能量级的划分和“目标锁定”等小细节, 提升孩子寻找之后的成就感,逐步提升专注力、记忆力、观察力三大能力。《我的第一本专注力训练书 》足足128页,让孩子一次玩得过瘾、找得开心。

2) 学会提问(原书第10版)

ask question

学会提问是一门很大的学问。批判性思维领域“圣经”之作!权威大师30年畅销不衰的经典!史上最有内涵的思维训练书!亚马逊思维科学领域no.1!俞敏洪高度推荐 美国大学生人手一本!打开心智,提早具备未来创新人才的核心竞争力!

3) 棚车少年(套装共8册)(中英双语)(当孩子遇到挫折,这本书能让他们笑着面对人生)

adversity

天下没有100%顺利的事,孩子总有一天会遇到挫折。遇到挫折该怎么办,怎么面对?读了这本书能让孩子笑着面对人生,不如买给孩子看看。这本书是中英双语,还能帮助孩子练习语文。《棚车少年》:亨利、杰西、维莉、班尼四兄妹从小就是孤儿,他们知道自己有一个爷爷在绿野镇,但是他们不喜欢他。为了躲避爷爷,孩子们在一个破旧的棚车里 安了家,开始相依为命的生活。他们积极向上,阳光开朗,不惧生活的挫折。不仅如此,他们还相互帮助,一起寻找生活的乐趣,在树林里安家、收留小狗望望、探 宝、自由赛……最后爷爷找到了他们,原来爷爷很年轻、慈祥、很爱他们。最后他们跟爷爷一起回家,过上幸福快乐的日子。

WordPress to Sina Weibo 微博 Automatic Posting

I recently discovered a way to post (automatically) from WordPress to Sina Weibo 微博(China’s version of twitter, which has more than half a billion users!)

The trick is to use IFTTT.com (If this then that).

Steps:

1) Setup up publicize for WordPress to Twitter. (WordPress.com can do this automatically).

2) Go to IFTTT.com, and set up a recipe from Twitter to Weibo. (There is a premade template for that, takes less than 5 minutes to sign up)

Done!

There may be a way for WordPress –> Weibo direct posting, I am still researching on that. (Update: Yes, there is a recipe for direct WordPress –> Weibo too!) It depends on whether you want a short summary, in which case WordPress –> Twitter –> Weibo may suit you better. If you want a full text, then WordPress –> Weibo is great. Or, you can use both!

Hope it is helpful!

weibo

无微不至:微博营销实战指南

《无微不至:微博营销实战指南》内容简介:企业如何利用微博进行营销?如何了解消费者的购买心理?如何把握微博的传播机制,发现用户的行为模式,找到有价 值的客户?如何挖掘数据价值,制定营销方案,实现营销的最佳效果?《无微不至:微博营销实战指南》从如何搭建企业微博营销平台、构建微博体系、塑造企业微 形象、选择微博营销模式,以及微博营销的技能、微博写作技巧等方面详尽地讲述微博营销的方法、技巧,具有实操性强,案例经典,拿来就能用的特点。在《无微 不至:微博营销实战指南》中,读者还会学到以下经典内容:微博营销已不是简单开个账户,发发帖子。微博传播永远是内容为王,无论是重口味,还是小清新,一 定要与草根文化血脉相通。写微博和说相声是一样的,要善于抖包袱,要在140字中写出跌宕起伏。10%的人影响了90%的人的购买行为,微博是影响他人购 买决策的一个有效工具。社交广告即将或者已经成为最主流的社会化营销解决方案。高质量的内容和互动永远是提高粉丝转发率、留住粉丝的不二法宝。中国移动、 中国电信应该如何做微博营销?《独唱团》爆单,快书包如何转危机为商机?如何打造企业官微?1000个真实的粉丝意味着什么?如何用微博编织人脉?微博内 容写作十大技巧是什么……

Chinese Math and Science Books

Just to introduce a few books that can simultaneously improve your child’s Math and Science knowledge, and Chinese at the same time!

The latest news is that China is building the Kra Canal, a news that would mark the beginning of the increased dominance of China in Southeast Asia, hence having a good grasp of Mandarin is no longer optional, but 100% compulsory if you want to have a slice of the pie of the jobs and benefits generated by China.

华文数学/科学书本

1)
可怕的科学•经典数学系列(套装共12册)(三度荣获国际科普图书最高奖)

horrible science

This series of “Horrible Science” Books is translated into Chinese, and is an award winning series of books. Highly recommended!

2)
小学奥数700题详解:3、4、5、6年级

math olympiad

700 Practice Problems for Math Olympiad! These books are very useful for GAT / DSA / GEP Preparation.

3)
走进奇妙的数学世界1-3(套装共3册)

math olympiad world of math

Into the world of Mathematics! 《走进奇妙的数学世界1-3(套装共3册)》内容简介:数学最让人困惑的是为什么这样和有什么用,很多人即使大学毕业也不明白,这套书完美地阐释了数学的 本质,把数学和生活紧密联系在一起。13种基本数学思想,层层深入,完美阐释数学的本质。以两个小矮人贯穿全文,图文并茂,讲故事、出谜题、做游戏,游戏 背后蕴藏数学概念让孩子以最简单、最科学的方式走近数学,爱上数学!不仅仅讲算术,更重在启发从不同角度看待事物、解决问题的思考方式,培养孩子的逻辑思 维能力,提高综合素质。

Finally, for readers of my blog who are new to Chinese, and wish to learn this 5000 year old language, I would recommend some books to learn Chinese for beginners here:

轻松学中文1(课本)(附CD光盘1张)

easy chinese

Learn Chinese in an easy manner! Easy steps to Chinese. (With CD)

Free USD 50 Amazon voucher (For Business and Engineering majors)

Hi, just to share a way to win a free USD 50 Amazon voucher!

This offer is only open to students from NUS, NTU, SMU; both Business and Engineering Bachelor Degree students, who have just completed their studies in 2015 or completing studies in 2016.

Details:

Greetings!

We, Universum, are currently conducting a research about career expectations of students. For this study, we are currently recruiting undergraduate students to participate in a 3-day online focus group.

If selected, the students will receive a USD 50 Amazon voucher after their active participation during the discussion. The online focus group will be scheduled from now to 14 June 2015, and will be active for 3 days. Selected students are encouraged to log in to participate actively during this period.

Interested students will just need to register here or http://goo.gl/forms/xp1OnFrXlQ. We will contact the students if they are selected. They will then be notified as soon as possible of the periods of the focus group and will receive further details of the interview’s topic.

Nadine Dinh

B2C Marketing and Relations Manager for APAC

A Graph Theory Olympiad Question Whose Answer is 1015056

April’s Math Olympiad Question was a particularly tough one, only four people in the world solved it! One from Japan, one from Slovakia, one from Ankara, and one from Singapore!

The question starts off seemingly simple enough:

In a party attended by 2015 guests among any 7 guests at most 12 handshakes had been
exchanged. Determine the maximal possible total number of handshakes.

However, when one starts trying out the questions, one quickly realizes the number of handshakes is very large, possibly even up to millions. This question definitely can’t be solved by trial and error!

This question is ideally modeled by a graph, and has connections to the idea of a Turán graph.

The official solution can be accessed here: http://www.fen.bilkent.edu.tr/~cvmath/Problem/1504a.pdf

 

Turan 13-4.svg
The Turán graph T(13,4)

 

To read more about Math Olympiad books, you may check out my earlier post on Recommended Math Olympiad books for self-learning.

Coursera Probability Course and Recommended Probability Book

Just completed the Coursera Probability Course by UPenn (University of Pennsylvania), lectured by Professor Santosh S. Venkatesh who is the author of the highly recommended book: The Theory of Probability: Explorations and Applications.

Coursera Review

The course isn’t very hard, it is very suitable for undergraduates and even high school students should be able to understand majority of the content. It actually overlaps with the A level syllabus in Singapore, and hence I would say that a 17-18 year old student would be able to grasp most of the concepts in this course.

The lecturer is very good at words, and his lectures are full of imagery and vivid descriptions. The homework is a little tricky, and hence would require some thought, even though the concepts tested are elementary (elementary in the sense that it doesn’t require calculus).

A sample of a tricky question is the “Six Saucer Question”: Six cups and saucers come in pairs: there are two cups and saucers that are red, white, and blue. If the cups are placed randomly onto the saucers (one each), find the probability that no cup is upon a saucer of the same color.

It is very tricky and to get it correct on the first try is a major accomplishment.

Overall, this Coursera Course is highly recommended, and students should try to take it the next time it comes out!

Chinese Remainder Theorem History (韩信点兵)

I have written a guest post on https://chinesetuition88.wordpress.com on the very fascinating Chinese Remainder Theorem and its History (韩信点兵). Do check it out, you will be amazed at the genius of Chinese General Han Xin.

Students who are interested in Chinese Tuition may check out https://chinesetuition88.wordpress.com for more details.

chinesetuition88's avatarChinese Tuition Singapore

淮安民间传说着一则故事——“韩信点兵”,其次有成语“韩信点兵,多多益善”。韩信带1500名兵士打仗,战死四五百人,站3人一排,多出2人;站5人一排,多出4人;站7人一排,多出6人。韩信马上说出人数:1049。

Translation:

In Ancient China, there was a General named Han Xin, who led an army of 1500 soldiers in a battle. An estimated 400-500 soldiers died in the battle. When the soldiers stood 3 in a row, there were 2 soldiers left over. When they lined up 5 in a row, there were 4 soldiers left over. When they lined up 7 in a row, there were 6 soldiers left over. Han Xin immediately said, “There are 1049 soldiers.”

Amazing! How did Han Xin do that?

Han Xin was not only a brilliant mathematician and general, he was also a very magnanimous guy full of wisdom.

Once, when he was suffering from hunger, he met a woman who provided him with food. He promised to repay her for her kindness after he had made great achievements in life, but it was rebuffed by her…

View original post 342 more words

Cheryl’s Birthday Problem

We all know by now Singapore Math is not easy, but here is the viral Singapore Math problem that took the world by storm!

Question:

Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl marks 10 possible dates: May 15, May 16, May 19, June 17, June 18, July 14, July 16, August 14, August 15, or August 17.

Then Cheryl tells Albert the month of her birthday, but not the day. She tells Bernard the day of her birthday, but not the month. Then she asked if they can figure it out.

Albert: I don’t know when Cheryl’s birthday is, but I know Bernard doesn’t know either.

Bernard: At first I didn’t know when Cheryl’s birthday is, but now I know.

Albert: If you know, then I know too!

When is Cheryl’s birthday?

Source: http://www.vox.com/2015/4/15/8420577/cheryls-birthday-singapore-math

There is a nice Numberphile video about it too.

Do give it a try! (The fun is in trying to solve the question)

Also, another fun part is sending this question to your friends!

Also see: Meet the mathematics lecturer behind ‘Cheryl’s birthday’ puzzle – See more at: http://www.straitstimes.com/news/singapore/more-singapore-stories/story/meet-the-mathematics-professor-behind-cheryls-birthday-p#sthash.qKZZtwpk.dpuf

To be honest, though Cheryl’s birthday puzzle is difficult, there are more challenging logic puzzles around. For a good challenge (and good practice), check out Puzzle Baron’s Logic Puzzles. It is a very good practice for children gearing up for Math Olympiad since they love to test logic questions in Math Olympiad.

Egyptian Math Mystery

Translation:

[The world’s most mysterious number is 142857.]

It is found in the ancient Egyptian Pyramids.

142857 x 1=142857

142857 x 2=285714

142857×3=428571

142857×4=571428

142857×5=714285

142857×6=857142

142857×7=999999

Amazing? Each multiple is a cyclic permutation of the original numer 142857.

You may read more about Egyptian mathematics in this wonderful book: Count Like an Egyptian: A Hands-on Introduction to Ancient Mathematics.

egypt math

3 of the Top Jobs in America involve Math

Although in Singapore currently doctors and lawyers are the top jobs, the trend is changing, starting with the most technologically advanced country – America. 3 of the top jobs in America are about Math. As the world becomes more dependent on technology (and hence mathematics), Mathematics will play a more prominent role in the global scene. Eventually the change will come to Singapore too, as more and more jobs require mathematical skills.

According to our Law Minister Mr Shanmugam, Singapore is facing a glut (excessively abundant surplus) of lawyers, which means that Singapore may not have so many jobs for lawyers. “The study of law provides an excellent training of the mind, so I don’t want to be seen as discouraging people… but you have to have a realistic understanding of the market, the economy, the total structure,” said Mr Shanmugam – See more at: http://www.straitstimes.com/news/singapore/more-singapore-stories/story/singapore-facing-glut-lawyers-shanmugam-20140817#sthash.BojzeqhX.dpuf

Hence, young students may want to consider a new discipline that is Math related, like Actuary, Math, or Statistics. To read up more about what true Mathematics is (it is very different from high school mathematics, where students just practice differentiation and integration), check out this book How to Think Like a Mathematician: A Companion to Undergraduate Mathematics.

Site: http://www.businessinsider.sg/best-jobs-of-2015-2015-4/#.VTEI7ZPoaKg

Perhaps if you had known that some of the best jobs of 2015 would require mathematical skills, you would’ve paid more attention in your high school algebra class.

Professions like actuary, mathematician, and statistician are three of the top jobs in America right now, according to CareerCast.com, a career guidance website that just released its 27th annual Jobs Rated report.

“Jobs in mathematics rank among the nation’s best jobs because they are financially lucrative, offer abundant opportunities for advancement, and provide the opportunity to do great work in a supportive environment,” says Tony Lee, publisher of CareerCast.com, in a press statement.

Here are the 10 best jobs of 2015:

2015 Rank Job Title Mid-level Income
1 Actuary $94,209
2 Audiologist $71,133
3 Mathematician $102,182
4 Statistician $79,191
5 Biomedical Engineer $89,165
mathematician
University of the Fraser Valley/flickr

Read more at: http://www.businessinsider.sg/best-jobs-of-2015-2015-4/#.VTEI7ZPoaKg

Math is Forever (Spanish)

With humor and charm, mathematician Eduardo Sáenz de Cabezón answers a question that’s wracked the brains of bored students the world over: What is math for? He shows the beauty of math as the backbone of science — and shows that theorems, not diamonds, are forever. In Spanish, with English subtitles.

Yes, indeed, 1000 years from now, students will still be learning Pythagoras’ Theorem, while other fragments of human knowledge would have faded away.

Check out also this book: Arithmetic and Algebra Again: Leaving Math Anxiety Behind Forever, suitable for students who really need some encouragement and motivation to overcome fear of math! Albert Einstein once said, “You never fail until you stop trying.” Hence, even if you have not done well in math for the past years, there is still hope, don’t give up!

April Fools Video Prank in Math Class

Check out this really funny video on a April Fools Prank during a Math Class!

The teacher played a trick on his math class for April Fool’s Day. In this one, he’s showing a “homework help” video that gets some trigonometry wrong.

Looking for more Math Jokes? Check out the book below!

Math Jokes 4 Mathy Folks

Permutation Math Olympiad Question (Challenging)

March’s Problem of the Month was a tough one on permutations. Only six people solved it! (Site: http://www.fen.bilkent.edu.tr/~cvmath/Problem/problem.htm)

The question goes as follows:

In each step one can choose two indices 1\leq k,l\leq 100 and transform the 100 tuple (a_1, \cdots, a_k, \cdots, a_l, \cdots, a_{100}) into the 100 tuple (a_1, \cdots, \frac{a_k}{2}, \cdots, a_l+\frac{a_k}{2}, \cdots, a_{100}) if a_k is an even number. We say that a permutation (a_1, \cdots, a_{100}) of (1, 2, \cdots, 100) is good if starting from (1,2,\cdots, 100) one can obtain it after finite number of steps. Find the total number of distinct good permutations of (1, 2, \cdots, 100).

The official solution is beautiful and uses induction.

 

Personally, I used a more brute force technique to get the same answer using equivalence class theory which I learnt in my first year of undergraduate math! It is not so bad in this question, since n is only 100, but for higher values of n the approach in the official solution would be better.

If you are looking for recommended Math Olympiad books, check out this page. In particular, if you are looking for more Math Olympiad challenges, do check out this book Mathematical Olympiad Challenges. In fact, any book by Titu Andreescu is highly recommended as he is the legendary IMO (International Math Olympiad) coach that led the USA team to a perfect score!

What’s Math Got to Do with It?: How Teachers and Parents Can Transform Mathematics Learning and Inspire Success

Recently, Professor Jo Boaler released her new book What’s Math Got to Do with It?: How Teachers and Parents Can Transform Mathematics Learning and Inspire Success.

The minute it came out, it became an instant best seller on Amazon. Currently, there are some issues on Math education in the United States, due to the very controversial syllabus called Common Core. Professor Jo Boaler attempts to address these controversies and give suggestions and advice to parents.

I totally agree with Professor Jo’s viewpoint that the first step to engage students in math learning is via practical means and showing them how mathematics is useful and relevant to their lives. Next is to always adopt a “growth mindset”, that no matter how weak or strong a child is in math, it is always possible to improve. Just having this mindset makes a huge difference. I took Prof. Jo Boaler’s online course on “How to Learn Math“, and what she said actually makes perfect sense. Hope a new generation appreciative of math will emerge due to new research on how to best learn Math, which Prof. Jo Boaler (PhD in Math Education) is an expert in.

Without further ado, I will link Prof. Jo Boaler’s introduction to her own book:

Hi Everyone,

I wanted you to be the first to know that my new book: What’s Math Got to Do With It:? How Teachers and Parents Can Transform Mathematics Learning and Inspire Success has just hit the bookstores and of course Amazon and other online outlets.

You can now get a copy here: What’s Math Got to Do with It?: How Teachers and Parents Can Transform Mathematics Learning and Inspire Success

The changes from the original book include:

2 new chapters
A focus on mindset
Ideas for the Common Core
An infusion of new research through the book

Why not buy the book for your principal? Or your colleagues? your family? your students’ parents? or others who you think may need to understand the nature of good mathematics teaching? You may need people to know the research evidence behind what you are doing, as well as get some new ideas yourself.

For youcubers in the UK there will be a new edition of The Elephant in the Classroom coming out in the Autumn, we will let you know when, of course.

I also wanted you to know about some book signings that are planned:

Friday April 3 Portsmouth, New Hampshire. The Exeter High School Auditorium 7-8.30pm talk followed by book signing. See:

http://www.seacoastonline.com/article/20150330/NEWS/150339887/101019/NEWS

At NCSM:
Monday April 13th Boston, NCSM Following Jo’s keynote talk

At NCTM:
Thursday April 16th, 11.30 After Jo’s networking session.

We will also be arranging a book signing in the San Francisco bay area soon too.

I hope to see you at one of them. Below is our youcubed team reading the book yesterday 🙂

Viva La Revolution

Jo

The Math of Shuffling Cards

Previously, the first YouTube video wasn’t working. I have added a new link to the interesting “Looking at Perfect Shuffles” video. 🙂

mathtuition88's avatarMathtuition88

A magic trick based on the “Perfect Shuffle”. Featuring Professor Federico Ardila. I watched his videos on Hopf Algebras while learning the background material for my honours project on Quantum Groups.

Mathemagician Persi Diaconis discusses which is the best way to shuffle: Overhand shuffle, Riffle Shuffle, or “Smoosh” Shuffle? Watch the video to find out!

Magical Mathematics: The Mathematical Ideas That Animate Great Magic Tricks is an interesting book by Professor Diaconis, featuring Magic Tricks that have a mathematical background! This book is a great idea for a gift for students, teachers, or friends!

View original post

NUS High Selection Test (DSA)

Official Website: http://www.nushigh.edu.sg/admission-n-outreach/admissions/eligibility-n-admissions-process

The official website, unfortunately, doesn’t tell much about how the NUS High Selection Test / DSA is like, in particular the format of the exam.

However, from online sources from students who took the test, we can have a glimpse of what the NUS High Selection Test (DSA) is like.

Disclaimer: I have not taken the NUS High Selection Test (DSA) before, and I am only listing down suggested format of the tests based on the online sources. I have taken the GEP Selection Test (both round 1 and round 2) though, at Primary 3.

Source 1: http://wwwdontmesswith6a.blogspot.sg/2011/06/nus-high-selection-test.html

This is a highly reliable blog post by the sister of Lim Jeck, a highly skilled Math Olympiad Participant who has achieved perfect score at IMO. From the blog post, we can tell that:

  • The Math Paper is 1 and a half hours.
  • Math Paper is “ok” (easier than NMOS) Do take note that the blogger is very good at math, so “easy” is subjective.
  • Math Paper has 7 pages, inclusive of cover page and last page.
  • 23 Non-MCQ questions, where you have to shade the integer answer. (Do bring a pencil!)
  • “The first few Math questions are easy, like P6 Math questions. One of the easiest Math questions is, the average of 3 numbers is given, you add another 2 numbers and you get another given average, you have to find the sum of the 2 numbers added. There are varying marks for different questions. I think the harder questions carry 4 marks.”
    (Again, easy is subjective, what is easy for a Olympiad Gold Medalist may not be easy at all)
  • “Total marks for Maths and Science are 55 and 30 respectively.For Maths, max of answer shades is 4, so max answer may be 9999. Maths questions carry 1 mark, 2 marks, 3 marks and 4 marks. Think Q23 (last qn) is a 4-mark question.”
    (We can assume that due to the format of this test, all answers are integers!)

Read more at http://wwwdontmesswith6a.blogspot.sg/2011/06/nus-high-selection-test.html to get an idea of the original post and how the Science NUS High DSA (supposedly more difficult than the Math NUS High DSA) is like.

To deal with difficult NUS High DSA problems (last few questions of the Selection Test), most likely the student has to be trained in Math Olympiad. A book like The Art of Problem Solving Volume 1: The Basics AND Basics Solution Manual (2 Volume Set would be ideal in beginning the journey in Math Olympiad. Note that Math Olympiad is nothing like normal school math, and even a fresh university graduate in a math-related major say Engineering/Accounting would have great problems solving a Primary 6 Math Olympiad question, if he doesn’t have the necessary Math Olympiad background!

If you are also interested in preparing for GEP (Primary 3 or Secondary 1 intake), do check out my most popular page on Recommended Books for GEP.

Other blogs with info on the NUS High DSA Selection Test:

Update (2016): Check out this Pattern Recognition (Visual Discrimination) book that is a guided tutorial for training for GEP / DSA Tests!

The Math of Shuffling Cards

A magic trick based on the “Perfect Shuffle”. Featuring Professor Federico Ardila. I watched his videos on Hopf Algebras while learning the background material for my honours project on Quantum Groups.

Mathemagician Persi Diaconis discusses which is the best way to shuffle: Overhand shuffle, Riffle Shuffle, or “Smoosh” Shuffle? Watch the video to find out!

Magical Mathematics: The Mathematical Ideas That Animate Great Magic Tricks is an interesting book by Professor Diaconis, featuring Magic Tricks that have a mathematical background! This book is a great idea for a gift for students, teachers, or friends!

Mathematicians have prevented a world disaster, behind the scenes

Recently, after taking the Coursera course on Cryptography, I had a better appreciation of mathematics and the role of cryptography in our modern society.

I was pleased to read this article Quantum compute this: Mathematicians build code to take on toughest of cyber attacks, and Washington State University mathematicians have designed an encryption code capable of fending off the phenomenal hacking power of a quantum computer.

The quantum computer, though not yet invented, is widely believed to be available soon in the next few years. In the hands of hackers, the quantum computer would be a formidable weapon as current cryptographic methods are extremely vulnerable to the quantum computer as it can factor numbers extremely quickly, leading to number theoretic codes being broken.

What would happen if a Quantum Computer is built

Quantum computers are near

Quantum computers operate on the subatomic level and theoretically provide processing power that is millions, if not billions of times faster than silicon-based computers. Several companies are in the race to develop quantum computers including Google.

Internet security is no match for a quantum computer, said Nathan Hamlin, instructor and director of the WSU Math Learning Center. That could spell future trouble for online transactions ranging from buying a book on Amazon to simply sending an email.

Hamlin said quantum computers would have no trouble breaking present security codes, which rely on public key encryption to protect the exchanges.

In a nutshell, public key code uses one public “key” for encryption and a second private “key” for decoding. The system is based on the factoring of impossibly large numbers and, so far, has done a good job keeping computers safe from hackers.

Quantum computers, however, can factor these large numbers very quickly, Hamlin said. But problems like the knapsack code slow them down.

Fortunately, many of the large data breaches in recent years are the result of employee carelessness or bribes and not of cracking the public key encryption code, he said.

Hence, when many people say mathematics is useless, they are actually extremely wrong, as mathematics permeates every aspect of life! Even though maths like calculus is not directly used in everyday life, it is part of our phone, computer, and every part of the modern lifestyle.

Kudos to the mathematicians who have averted a world disaster, before quantum computers are even invented!

If you are interested in what a quantum computer is, and what it can do (it is so powerful that whoever has one would hold the keys to the entire internet), check out this book Schrödinger’s Killer App: Race to Build the World’s First Quantum Computer.

Written by a renowned quantum physicist closely involved in the U.S. government’s development of quantum information science, Schrödinger’s Killer App: Race to Build the World’s First Quantum Computer presents an inside look at the government’s quest to build a quantum computer capable of solving complex mathematical problems and hacking the public-key encryption codes used to secure the Internet. The “killer application” refers to Shor’s quantum factoring algorithm, which would unveil the encrypted communications of the entire Internet if a quantum computer could be built to run the algorithm. Schrödinger’s notion of quantum entanglement—and his infamous cat—is at the heart of it all.

Vector Subspace Question (GRE 0568 Q3)

This is an interesting question on vector subspaces (a topic from linear algebra):

Question:
If V and W are 2-dimensional subspaces of \mathbb{R}^4, what are the possible dimensions of the subspace V\cap W?

(A) 1 only
(B) 2 only
(C) 0 and 1 only
(D) 0, 1, and 2 only
(E) 0, 1, 2, 3, and 4

To begin this question, we would need this theorem on the dimension of sum and intersection of subspaces (for finite dimensional subspaces):

\dim (M+N)=\dim M+\dim N-\dim (M\cap N)

Note that this looks familiar to the Inclusion-Exclusion principle, which is indeed used in the proof.

Hence, we have \dim(M\cap N)=\dim M+\dim N-\dim (M+N)=4-\dim (M+N).

\dim (M+N), the sum of the subspaces M and N, is at most 4, and at least 2.

Thus, \dim (M\cap N) can take the values of 0, 1, or 2.

Answer: Option D

If you are looking for a lighthearted introduction on linear algebra, do check out Linear Algebra For Dummies. Like all “For Dummies” book, it is not overly abstract, rather it presents Linear Algebra in a fun way that is accessible to anyone with just a high school math background. Linear Algebra is highly useful, and it is the tool that Larry Page and Sergey Brin used to make Google, one of the most successful companies on the planet.

Professor Stewart’s Incredible Numbers

Amazon just informed me of a new book which is the #1 New Release Math Book on Amazon!

The book is titled: Professor Stewart’s Incredible Numbers.

At its heart, mathematics is about numbers, our fundamental tools for understanding the world. In Professor Stewart’s Incredible Numbers, Ian Stewart offers a delightful introduction to the numbers that surround us, from the common (Pi and 2) to the uncommon but no less consequential (1.059463 and 43,252,003,274,489,856,000). Along the way, Stewart takes us through prime numbers, cubic equations, the concept of zero, the possible positions on the Rubik’s Cube, the role of numbers in human history, and beyond! An unfailingly genial guide, Stewart brings his characteristic wit and erudition to bear on these incredible numbers, offering an engaging primer on the principles and power of math.

Previously, I read Galois Theory, Third Edition (Chapman Hall/Crc Mathematics), also by Ian Stewart, and I have to say his style is very accessible to the average reader. Not overly technical or abstract, he actually explains Galois Theory in as concrete a way as possible, which is not easy, since Galois Theory is one of the most abstract topics in mathematics.

I read the Third Edition, featured above, but lately there is a newer and better fourth edition: Galois Theory, Fourth Edition.