11.
One pipe can fill a tank three times as fast as another pipe. If together the two pipes can fill the tank in 36 minutes, then the slower pipe alone will be able to fill the tank in:

12.
A large tanker can be filled by two pipes A and B in 60 minutes and 40 minutes respectively. How many minutes will it take to fill the tanker from empty state if B is used for half the time and A and B fill it together for the other half?

13.
A tap can fill a tank in 6 hours. After half the tank is filled, three more similar taps are opened. What is the total time taken to fill the tank completely?

14.
Three taps A, B and C can fill a tank in 12, 15 and 20 hours respectively. If A is open all the time and B and C are open for one hour each alternately, the tank will be full in:

15.
Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. The number of hours taken by C alone to fill the tank is:

16.
Water is continuously supplied from a reservoir to a locality at the steady rate of 10000 liters per hours. When delivery exceeds demand the excess water is stored in a tank. If the demand for 8 consecutive three hour periods is 10000, 10000, 45000, 25000, 40000, 15000, 60000 and 35000 liters respectively, what will be the minimum capacity required of the water tank (in thousand liters)to meet the demand and avoid any wastage?

17.
A pipe can fill a tank in x hours and another pipe can empty it in y (y > x) hours. If both pipes are open, in how many hours will the tank is filled?

18.
A pipe can fill a tank with water in 3 hours. Due to leakage in bottom, it takes $$3\frac{1}{2}$$ hours to fill it. In what time the leak will empty the completely filled tank?

19.
Two pipe can fill a cistern in 3 hours and 4 hours respectively and a waste pipe can empty it in 2 hours. If all the three pipes are kept open, then the cistern will be filled in-

20.
$$\frac{3}{4}$$ part of the tank is full of water. When 30 litres of water is taken out, the tank becomes empty. The capacity of the tank is -