The number of half-lives needed for a radioactive element to decay to about 6% of its original activity is (choose nearest number):
A)2
B)3
C)4
D)5
E)6

Question

Quizplus · Accepted Answer

The number of half-lives needed for a radioactive element to decay to about 6% of its original activity is 3. This is because each half-life reduces the activity by half, so after 3 half-lives, the activity will be reduced to 1/8 of its original value, which is approximately 6%.

The Number of Half-Lives Needed for a Radioactive Element to Decay