Question

A substance has a half-life of 5 years, how much of the initial sample remains after 15 years?

• A. One-fourth (1/4)
• B. One-sixteenth (1/16)
• C. One-half (1/2)
• D. One-fifth (1/5)
• E. One-eighth (1/8)

Answer 1

The correct option is E One-eighth (1/8)

A substance has a half-life of 5 years.
The number of half life periods in 15 years $=\frac{15}{5}=3$.
$\frac{1}{2^3}=\frac{1}{8}$ of the initial sample remains after 15 years.