Question

Two taps can fill a tank in 4 and 5 hours respectively, while a third tap can drain 320 liters water from it in 1 hour. If all the three taps are opened together then the completely filled tank is emptied in 20 hours. What is the capacity of the tank?

Answer 1

Part of the tank that can be filled by the two filler taps  = (  1/30 + 1/20) = 1/12

∴ The two taps can fill the tank in 12 minutes.

half of the tank will be filled in 6 minutes.

The time taken by the remaining half of the tank to be filled when the outlet pipe is open =(24−6) min =18 min.

Part of that half of the tank that can be emptied in 1 hour = 1/6 - 1/18 = 1/9

∴ Time taken to empty half of the cistern =9 minutes

∴ Capacity of the tank =100×9×2=1800 liters.