The half-life of radium is about 1600 years. If a rock initially contains 1 g of radium, the amount left after 8000 years will be about:
A) 200 mg
B) 63 mg
C) 31 mg
D) 16 mg
E) less than 1 mg

Question

Quizplus · Accepted Answer

The half-life of radium is 1600 years, so after 8000 years (which is 5 half-lives), the amount of radium left is (1/2)^5 of the original amount. This equals 1/32 of 1 g, which is approximately 31 mg.

The Half-Life of Radium Is About 1600 Years