Question

A sample of U-235 has a half-life of 700 million years. What fraction of the parent material will remain after 2800 million years?

A. 1/2
B. 1/4
C. 1/8
D. 1/16
E. 1/32

Answer 1

After 2800 million years, 1/16 of the parent material will remain.

Step-by-step explanation:

The fraction of the parent material that will remain after 2800 million years can be calculated by dividing the time by the half-life. In this case, 2800 million years divided by 700 million years gives us 4 half-lives. Each half-life reduces the parent material by half. So, after 4 half-lives, the fraction of the parent material that will remain is 1/2 x 1/2 x 1/2 x 1/2 = 1/16.