A pipe can fill a tank in 15 hours. Due to leakage in the bottom it is filled in 20 hours. If the tank is full, and the pipe is closed, how much time will the leak take to empty the entire tank?

60 hrs

A+ = 15 hrs, A + (-B) = 20 hrs,

⇒ Therefore, Time required by B to empty whole tank = \(\frac{60}{1}\) = 60 hrs.        ..(\(\frac{Work}{Efficiency}\) = Time)