Question

Half-life period of a substance is $1600\min$. How much fraction of the substance will remain after $6400\min$?

• A. $\frac{1}{16}$
• B. $\frac{1}{4}$
• C. $\frac{1}{8}$
• D. $\frac{1}{2}$

Answer 1

Answer: (A)

Given, half-life period $=1600\min$
Time $=6400\min$
Number of life $(n)=\frac{\text{ time }}{\text{ half-life period }}$
$=\frac{6400}{1600}=4$
Amount left $=\frac{1}{2^4}=\frac{1}{16}$
Alternate method Initial amount Half-life period Amount left
$11600mm1/21/21600mm1/41/41600mm1/81/81600min1/166400$