A cistern can be filled in 9 hours. But due to a leak, it takes one hour more. If the cistern is full, in what time will it become empty due to the leak?

Correct option is D

Given:

Pipe A can filled the tank = 9 hours 

With leakage Pipe A can fill the tank = 10 hours 

Solution

Let the total capacity of the tank = 90 unit 

then efficiency of Pipe A = 90\9 = 10 unit /hours 

Efficiency of Pipe A and leakage = 90/10 = 9 unit\hours

Efficiency of Leakage = (10 - 9) unit\hours  = 1 unit\hours

Then the leakage fill empty the full tanke = 90/1 = 90 hours