Pipes A and B can empty a full tank in 18 hours and 24 hours respectively. Pipe C alone can fill the tank in 36 hours. If the tank is (5/6) full and all the three pipes are open together, then in how many hours will the tank be emptied?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 12
All the pipes together, in 1 hour, can empty 1/18 + 1/24 - 1/36 = (4 + 3 - 2)/72 = 5/72th of the full tank
So, together they can empty the full tank in 72/5 hours
So 5/6 of the tank is emptied in 5/6 x 72/5 = 12 hours