Question

The half-life for a 100-gram sample of radioactive element X is 5 days. How much of element X remains after 10 days have passed?

A.
25 g

B.
50 g

C.
75 g

D.
100 g

Answer 1

After 5 days: 100 → 50 g (one half-life).
After 10 days (two half-lives): 50 → 25 g.

Answer: A. 25 g