Question

A swimming pool can be filled in 4 hours by 8 pumps of the same type how many such pumps are required, if the pool is to be filled in $2\frac{2}{3}$ hours?

Answer 1

A swimming pool can be filled in 4 hours by 8 pumps.
Let $x$ be the number of pumps required to fill the water in $2\frac{2}{3}=\frac{8}{3}$ hours.
As number of hours decreases then the number of pumps has to be increase. So, its inverse variation.
Thus, $\frac{x}{4}=\frac{8}{\frac{8}{3}}$
$\Rightarrow x=8\times \frac{3}{8}\times 4$
$=4\times 3$
$\therefore x=12$ pumps required to fill the water in swimming pool.