Question

A tank can be filled by 5 pipes in 80 minutes. How long will it take to fill the tank by 8 pipes of the same size?

Answer 1

The time period to fill a tank decreases as the number of pipes increases.

So, the number of pipes and time period are in inverse proportion.

If quantities $x$ and $y$ are in inverse proportion,

$\frac{x_1}{x_2}=\frac{y_2}{y_1}$

Here, let $x_1=5,y_1=80,x_2=8$, and $y_2$ to be found.

$\frac{5}{8}=\frac{y_2}{80}$
$y_2=\frac{5\times 80}{8}=5\times 10=50$

It will take 50 minutes to fill the tank using 8 pipes.