A tank has a leak which would empty the completely filled tank in 10 hours. If the tank is full of water and a tap is opened which admits 4 litres of water per minute in the tank , the leak takes 15 hours to empty the tank. How many litres of water does the tank hold?

Question: A tank has a leak which would empty the completely filled tank in 10 hours. If the tank is full of water and a tap is opened which admits 4 litres of water per minute in the tank , the leak takes 15 hours to empty the tank. How many litres of water does the tank hold?

Solution:
Let the total capacity of the tank is 30 units.
The efficiency of Leakage(Pipe A) will be 30/10 = 3
And the efficiency of the leakage (Pipe A) and another Pipe (B) which is filling the tank will be 30/15 = 2

Pipe A is emptying at 3 units/hr and when filling pipe B started then the emptying rate will come down to 2 units/hr.
∴ Filling Pipe B efficiency is 3 - 2 = 1 unit/hr
Pipe B will be fill the tank in 30/1 = 30 hrs.

The filling rate of Pipe B per minute is 4 litter
∴ Total Capacity of tank will be = (4 × 60) × 30 = 7200 litters.