An inlet pipe can fill a water storage tank in 11 hours and an outlet pipe can empty the completely filled tank in 15 hours .If both pipes opened simultaneously. The time taken to fill the empty tank (in hrs) is :
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. .
Time required for the inlet pipe to fill the tank = 11 hours
Time required for the outlet pipe to empty the tank = 15 hours
LCM of 11 and 15 = 165
Let the capacity of the tank be 165 units.
The rate of inlet pipe = 165/11 = 15 units/hour
The rate of outlet pipe = 165/15 = 11 units/hour
When both pipes are open, the net rate of filling is the difference between the inlet and outlet rates = 15 - 11 = 4 units/hour
Time required to fill the tank = 165/4 = hours
Therefore, the time taken to fill the empty tank is hours.