Question

A 320g sample of a substance called Iodine-131 is stored in a laboratory for 40 days. At the end of this period, only 7.5g remains. What is the half-life of Iodine-131?

Answer 1

If the half-life is k days, then
(1/2)^(40/k) = 7.5/320
k = 7.387