**Important Questions On Pipes and Cisterns**

**1**. Two pipes can fill a cistern in 20 and 30 minutes each respectively. When both the pipes were opened together to fill the cistern, it took 3 minutes longer than usual to fill up the cistern because of a leakage through a hole in the bottom of the cistern. If the cistern is full, in how many minutes, it will get emptied because of the leakage?

**2**. A cistern has two pipes. One can fill it in 8h and other can empty it in 5 h. In how many hours will the cistern be **emptied** if both the pipes are opened together when ¾ of the cistern is already full of water?

B. 10 h

C. 6 h

D.

**3**. A cistern can be filled by two supply pipes in 20 minutes and 30 minutes respectively. but a waste pipe can empty it in an hour. Both the supply pipes were opened together to fill the empty cistern, but by mistake, the waste pipe was also open. How much later was the waste pipe closed, if the cistern is filled in 14 minutes?

B. 8 minutes

C. 10 minutes

D. 12 minutes

**4**. Two pipes A and B can fill a cistern in minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after:

B. 9 min

C. 10 min

D. 15 min

**5**. Two pipes can fill a cistern in 8 and 12 hours respectively. The pipes are opened simultaneously and it is found that due to leakage in the bottom of the cistern, it takes 72 minutes extra for the cistern to be filled up. When the cistern is full, in what time the leak empty it?

B. 48 hours

C. 24 hours

D. 6 hours

**6**. A cistern can be filled by two pipes A and B in 20 and 30 minutes respectively. Both the pipes are opened together when the cistern is empty, but after some time A is stopped and the cistern is filled in 18 minutes is all. The time (in min) after which A is stopped, is

B. 12

C. 6

D. 8

**7**. Two pipes, P and Q can fill a cistern in 15 and 18 minutes respectively. If both are opened together and at the end of 3 minutes, Q is closed, how much longer will the cistern take to fill?

B. 9.50 minutes

C. 10.25 minutes

D. 10.50 minutes

B. 8 min

C. 10 min

D. 12 min

**9**. A cistern has 3 pipes *A*, *B* and *C*. *A* and *B* can fill it in 3h and 4 h respectively while *C* can empty the completely filled cistern in 1 h. If the pipes are opened in order at 3, 4 and 5 pm respectively. At What time will the cistern be empty?

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