a certain radioactive element has a half life of 31.2 years. in how many years will contamination reach 32% of the original contamination?

Answer 1

how many half lives in 32%
(1/2)^n = .32
n log .5 = log .32
n = -.495 / -.301 = 1.64 half lives
1.64 * 31.2 = ?

Answer 2

So the answer would be 51.168 years to get to 32% contamination?