Question

Cobalt-60 has a half-life of about 5 years.

How many grams of a 300 g sample will remain after 20 years?

A. 0.0625 g

B. 9.375 g

C. 18.75 g

D. 37.5 g

Answer 1

I think it's C.

Answer 2

do you know the definition of a half life?

Answer 3

oh wait, no need to go through that, you are correct

Answer 4

20 years is the equivalent of going through 4 half-lives

4 half lives is the equivalent of dividing by 2 4 times or dividing by 16

300/16=18.75

Answer 5

Thank you.