Question from http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=29&t=8315&start=780
The mass of particles of a certain radioactive chemical element is halved every 10 months. During a chemical experiment, the initial mass of particles of the chemical element is 3mg.
(i) write down an expression, in terms of t, for the mass of particles after t years.
(ii) Hence, find the value of t, if the mass is reduced to 0.046875 mg after t years.
How many 10 months are there in ? (Ans: )
Hence, the mass of particles after years is mg.
We need to solve .
Dividing by 3, we have .
Ln both sides, we have .
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