A pipe can fill a tank in 72 minutes. But there is a leak in the bottom of the tank due to which the tank is filled in 18 minutes more. Find in how many hours the leak can empty a full tank ?

Four pipes P, Q, R and S can fill a cistern in 25, 20, 50 and 40 hours respectively. The pipe Q was opened at 7 pm, P at 9 pm, S at 10 pm and R at 11 pm. When will the cistern be full?

Pipes  A and B are emptying pipes and can empty a tank in 6 hours and 16 hours, respectively. C is a filling a pipe. All the three pipes were opened together. They took 80 minutes to empty $$ {5\over 8}th$$ of the tank. Pipe C alone can fill the tank in:

Pipes A and B together can fill a tank in 16 hours, whereas pipe C alone can empty the full tank in 24 hours. A and B were opened together for 10 hours and then closed. Pipe C was then opened. The tank will now be emptied by C in:

If 20 taps can fill a tank in 14 hours, then how many times will 35 taps fill that tank?

A cistern can be filled by two pipes filling separately in 12 and 16 min respectively. Both pipes are opened together for a certain time but being obstructions, only 7/8 of full quantity water flows through the former and only 5/6 through the latter pipe. The obstructions, however, being suddenly removed, the cistern is filled in 3 minutes from that moment. How long was it obstructions before the full flow began? 

A pump can fill a cistern in 40 minutes and another pump can empty the filled up cistern in 1 hour. By mistake, without closing the second pump, the first pump is opened. The time in which the empty cistern will be filled up is

If all three pipes are opened for 2 minutes to fill the tank each alternatively in the sequence of A then C and then B.  Calculate water filled by pipes A is what % of water filled by pipe C?