Question

Suppose that you are given a 100 gram sample of a radioactive substance with a half-life of 32 days. How many grams will be left after 192 days?

Answer 1

192 days is 6 half-lives.

(1/2)^6 = 1/64

1/64 * 100 g = 1.5625 g

Answer 2

Carbon 14 has a half-life of 5,730 years. How long will it take for 400 grams of carbon 14 to decay to the point that only 100 grams are carbon 14.