Question

The half-life of cobalt 60 is 5.3 years. What fraction of a sample remains after 21.2 years?
A.
one half
B.
one quarter
C.
one eighth
D.
one sixteenth

Answer 1

\[\huge(\frac{1}{2})^{\frac{21.2}{5.3}}\]

Answer 2

21.2 / 5.3 = 4 times.

thus the answer is (1/2)^ 4
1/16