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?

Three pipes A , B and C takes 15, 24 and 36 minutes respectively to fill a tank. Pipe D can empty it in 1 hour. If all the four pipes are kept open then find the time taken to fill the tank. 

Three pipes A, B and C can fill a cistern 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 time taken by C alone to fill the cistern is_

Tank is normally filled in 8 hours but takes 2 hours longer to fill because of a leak in its bottom. If the cistern is full, in how many hours will the leak empty it? 

Pipes A and B can fill a tank in 43.2 minutes and 108 minutes, respectively. Pipe C can empty it at 3 litres/minute. When all the three pipes are opened together, they fill the tank in 54 minutes. The capacity (in litres) of the tank is:

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

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 ?

Three pipes, A B and C, can fill a cistern in 12, 18 and 24 minutes, respectively. If all the pipes are opened together for 7 minutes, what will be the volume of the water that overflows as the percentage of the total volume of the cistern?