Question

$3$ pumps who works $8$ hours per day empty the tank in $2$ days. How many hours per day will $4$ pumps use to empty the tank in $1$ day?

Answer 1

pumps hour per day days

3 8 2

4 ? 1

The number of pumps and hour per day are inversely related, i.e., if number of pumps increases then to finish the same task hour per day will decrease. Again number of pumps and number of days is inversely related.

So, required hour per day $=\frac{3}{4}\times \frac{2}{1}\times 8=12$