Question : Pipes A, B and C can fill a tank in 10, 15 and 30 hours, respectively. D is an emptying pipe which alone can empty the full tank in
Option 1: 50
Option 2: 40
Option 3: 60
Option 4: 45
Correct Answer: 50
Solution :
Let the capacity of the tank as
The rates at which pipes A, B, and C fill the tank are
The rate at which pipe D empties the tank is
In the first 3 hours, pipes A, B, and C together fill the tank with
After that, pipe D alone empties the tank in 30 hours, so it empties
Since the amount of water filled by pipes A, B, and C is equal to the amount of water emptied by pipe D.
Hence, the correct answer is 50.