Question

A radioactive material has a half life of 10 days. What fraction of the material would remain after 30 days.

• A. 0.5
• B. 0.25
• C. 0.125
• D. 0.33

Answer 1

Answer: (C)

0.125

Answer 2

$N = N_{0}\left( \frac{1}{2} \right)^{\frac{t}{T_{1/2}}} \Rightarrow \frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{\frac{30}{10}} = \frac{1}{8} = 0.125$.