Tag: puzzle

This is a favorite type of homeschool math challenging puzzle — The Snail question.

Question: An aquarium is 47 cm deep. A snail starts at the bottom of the aquarium. Each day, during the daytime the snail climbs up 8 cm, and during the nighttime the snail slides down 3 cm. How many days will it take for the snail to climb out of the aquarium?

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This is part of a series on Homeschool Math Challenging Puzzles, suitable for Grades 2-4. (Of course, students of other grades are also welcome to try them out.) The questions are suitable for:

• Homeschooling for gifted kids
• Preparation for GEP (Gifted Education Programme) screening and selection tests
• Preparation for Math Olympiad
• Puzzles for kids interested in math but find school work too easy.

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Solution:

A tempting answer would be 10 days. This is a trick! Those who get the answer “10 days” reason like this: each day the snail moves a net distance of 8-3=5 cm.

Hence, 47/5=9 R 2.

At the end of the 9th day, the snail moved 45 cm. Thus, rounding up will give 10 days as the answer. However, there is a tricky part to the question!

The correct answer is 9 days.

We can do a list:

Day 1 — 5 cm

Day 2 — 10 cm

Day 3 — 15 cm

…

Day 8 — 40 cm

Day 9 day time — 40 +8 = 48cm > 47 cm !!!

The snail is already out of the aquarium on Day 9!

Abby, Brian, Charles, Dennis and Eason have 50 stickers altogether.

Abby has the most stickers — she has 12 stickers.

In second place (tied) are Brian and Charles.

In third place is Dennis.

In fourth place is Eason, with 6 stickers.

How many stickers does Dennis have?

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This is part of a series on Homeschool Math Challenging Puzzles, suitable for Grades 2-4. (Of course, students of other grades are also welcome to try them out.) The questions are suitable for:

• Homeschooling for gifted kids
• Preparation for GEP (Gifted Education Programme) screening and selection tests
• Preparation for Math Olympiad
• Puzzles for kids interested in math but find school work too easy.

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For this type of questions, the easiest way to do is “trial and error”, also known as “guess and check”.

Firstly, lets check how many stickers B, C, and D have together:

50-12-6=32

B	C	D	Total (B+C+D)	Comments
9	9	14	32	Wrong! Since D is more than A
10	10	12	32	Wrong! Since D is tied with A
11	11	10	32	Correct!
12	12	8	32	Wrong! Since B, C is tied with A

For guess and check, the most important thing is to be systematic, rather than guess wildly. For instance, we can systematically increase our guesses for B, C.

We can see that the only logical answer is:

B= C=11

D=10

Answer: Dennis has 10 stickers.