Question

A radioactive sample starts with 800,000 undecayed nuclei. After 12 hours, 700,000 of the nuclei have decayed. What is the half-life of the sample?(1 point)
Responses

3 hours
3 hours
12 hours
12 hours
4 hours
4 hours
6 hours

Answer 1

4 hours.

Explanation:
The number of undecayed nuclei halved from 800,000 to 400,000 after 1 half-life (12 hours). Therefore, the half-life of the sample is 12 hours / 3 = 4 hours.