A pipe can fill a tank in  40 minutes. Due to a leakage in the bottom it took 60 minutes to fill the tank. How much time will it take for the leakage to empty the full tank ?

120 min

The correct answer is option (4) : 120 min

Let the leakage in the tank take x min. to empty the full tank

So, part of tank emptied by the leakage in 1 min $=\frac{1}{x}$

Part of tank filled by pipe in 1 min $=\frac{1}{40}$

Given when both pipe and leakage are working , it took 60 min to fill the tank.

So part of tank filled by both in 1 min $=\frac{1}{60}$

$∴\frac{1}{40}-\frac{1}{x}=\frac{1}{60}$

$\frac{1}{x}=\frac{1}{40}-\frac{1}{60}$

$x= 120$

Hence, the leakage will take 120 min to empty the full tank