Question

Sodium-24 has a half-life of approximately 15 hours. If only one-eighth of the sodium-24 remains, about how much time has passed?

A.
15 hours

B.
30 hours

C.
45 hours

D.
60 hours

Answer 1

Each half-life (15 h) reduces the amount by half. To get 1/8 = (1/2)^3 requires 3 half-lives: 3 × 15 h = 45 hours.

Answer: C (45 hours)