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
$1\, 1600 \,mm \,1 / 21 / 21600\, mm\, 1 / 41 / 41600\, mm\, 1 / 81 / 81600\, min\, 1 / 16\, 6400$