Question

A water tank can be filled in $7hours$ by $5$ equal-sized pumps working together. How much time will $7$ pumps take to fill it up?

Answer 1

Find the time taken by the pumps to fill the tank:

Here the number of pumps and time are in inverse proportion.

$5$ equal-sized pumps filled a tank in $7hours$

$1$ equal-sized pump filled a tank in $7\times 5hours=35hours$ ( less pumps, more time will take)

$7$ equal-sized pumps filled a tank in $\frac{35}{7}hours=5hours$ ( more pumps, less time will take)

Hence, 7 pumps will take $5hours$ to fill it up.