Question

After 10 days, 95% of a radioactive material has decayed

a) What is the half-life of the material?
b) How long will it take for there to be 15% of the original material left?

Answer 1

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Answer 2

Below

Explanation:

a) 1/2^n will show how much remains after 'n' halflives

95 % = .95

.95 = 1/2^n log both sides to find n = .07400058

so 10 days is .07400058 half lives

10 / .0740058 = half life = 135.1 days

b) .15 = 1/2^n shows n = 2.736 halflives

2.736 halflives * 135.1 days/halflife = 369.8 days