Question

In a camp, there is enough flour for 300 persons for 42 days. How long will the flour last, if 20 more persons join the camp?

Answer 1

For 300 persons flour is enough for 42 days.
Now, 20 more persons join the camp.
So, the total number of persons $=300+20=320$

$\begin{array}{ccc}\text{Number of people}& 300& 320\\ \text{Days food will last}& 42& x\end{array}$

The above is a case of inverse proportion.

$300\times 42=320\times x$

$\Rightarrow x=\frac{300\times 42}{320}$

$\Rightarrow x=\frac{15\times 21}{8}=\frac{315}{8}=39\frac{3}{8}$ days