Madhya Pradesh Police Exam Model Paper 8

Given:
A tap can fill a pond in 24 hours, and due to a leakage in the bottom it is filled in 36 hours
Concept:
If a tap can fill a tank in x hours, then the tank filled by the tap in 1 hour = 1/x of the total tank.
Calculation:
Part of pond emptied by leak in an hours $=\frac{1}{36}-\frac{1}{24}$
$\Rightarrow \frac{2-3}{72}=-172$
Time taken in emptying the full pond = 72 hours
Required time $=72/2=36$ hours
∴ The required time is 36 hours.