SOLUTION: The half life of a radioactive substance is 2 hours. (a)What percentage of an initial sample will remain after 1 hour? (b)What percentage of an initial sample will remain after

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Question 836622: The half life of a radioactive substance is 2 hours.
(a)What percentage of an initial sample will remain after 1 hour?
(b)What percentage of an initial sample will remain after 7 hours?
I know the half life is the time it takes for a substance to disintegrate but I cant seem to solve the problem. Please help!
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
The half life is the amount of time for half of the substance to disintegrate.

Since the sample decays exponentially, the amount A(t) of the substance as a function of time t (in hours) is given by



where k is a positive constant. The half-life is 2 hours. Assume A_0 = 1. Then



Substitute this value of k, as well as t = 1, t = 7, to find the answers to (a) and (b).