Question

Plutonium decays with a half life of $24,000$ years. If plutonium is stored for $72,000$ years, the fraction that remains is:

• A. $1/2$
• B. $1/4$
• C. $1/6$
• D. $1/8$

Answer 1

The correct option is D $1/8$

$t_{1/2}=24000yrs$

It is stored for 3 half-lives.

Fraction remaining is $(\frac{1}{2}{)}^3$$=\frac{1}{8}$