Pipes and Cisterns aptitude questions and answers for competitive exams. Pipes and Cisterns MCQs for test preparation and entry tests. Pipes and cisterns mcq with answers, Pipes and cisterns mcq pdf download and mathematics mcqs with answers pdf.

## Pipe A can fill a tank in 16 minutes and pipe B cam empty it in 24 minutes. If both the pipes are opened together after how many minutes should pipe B be closed, so that the tank is filled in 30 minutes ?

A. 24

B. 23

C. 20**D. None of these**Explanation:

Let the pipe B be closed after x minutes.

30/16 – x/24 = 1 => x/24 = 30/16 – 1 = 14/16

=> x = 14/16 * 24 = 21.## Pipe A can fill a tank in 6 hours. Due to a leak at the bottom, it takes 9 hours for the pipe A to fill the tank. In what time can the leak alone empty the full tank ?

A. 17 hours

**B. 18 hours**C. 16 hours

D. 15 hoursExplanation:

Let the leak can empty the full tank in x hours 1/6 – 1/x = 1/9

=> 1/x = 1/6 – 1/9 = (3 – 2)/18 = 1/18

=> x = 18.## A tank is filled in eight hours by three pipes A, B and C. Pipe A is twice as fast as pipe B, and B is twice as fast as C. How much time will pipe B alone take to fill the tank ?

A. 32 hours

B. 36 hours

C. 24 hours**D. 28 hours**Explanation:

1/A + 1/B + 1/C = 1/8 (Given)

Also given that A = 2B and B = 2C

=> 1/2B + 1/B + 2/B = 1/8

=> (1 + 2 + 4)/2B = 1/8

=> 2B/7 = 8

=> B = 28 hours.## Two pipes A and B can fill a tank in 20 and 30 minutes respectively. If both the pipes are used together, then how long will it take to fill the tank ?

A. 25 min

B. 50 min**C. 12 min**D. 15 minExplanation:

Part filled by A in 1 min. = 1/20

Part filled by B in 1 min. = 1/30

part filled by (A + B) in 1 min. = 1/20 + 1/30 = 1/12.

Both the pipes can fill the tank in 12 minutes.## 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 ?

A. 4 hrs

B. 4 hrs 15 min**C. 3 hrs 45 min**D. 3 hrs 15 min## A water tank is two-fifth full. Pipe A can fill a tank in 10 minutes and pipe B can empty it in 6 minutes. If both the pipes are open, how long will it take to empty or fill the tank completely ?

A. 9 min. to empty

B. 9 min. to full**C. 6 min. to empty**D. 6 min. to full## Pipe A can fill a tank in 5 hours, pipe B in 10 hours and pipe C in 30 hours. If all the pipes are open, in how many hours will the tank be filled ?

**A. 3**B. 3.5

C. 2.5

D. 2Explanation:

Part filled by A + B + C in 1 hour = 1/5 + 1/10 + 1/30 = 1/3

All the three pipes together will fill the tank in 3 hours.

## Pipes A and B can fill a tank in 5 and 6 hours respectively. Pipe C can empty it in 12 hours. If all the three pipes are opened together, then the tank will be filled in ?

A. 2 8/11 hours

B. 4 1/2 hours

C. 1 13/17 hours**D. 3 9/17 hours**Explanation:

Net part filled in 1 hour = 1/5 + 1/6 – 1/12 = 17/60

The tank will be full in 60/17 hrs, i.e., 3 9/17 hrs.

## A pump can fill a tank with water in 2 hours. Because of a leak, it took 2 1/3 hours to fill the tank. The leak can drain all the water of the tank in ?

A. 7 hrs

B. 8 hrs**C. 14 hrs**D. 4 1/3 hrsExplanation:

Work done by the tank in 1 hour = (1/2 – 1/3) = 1/14 Leak will empty the tank in 14 hrs.

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

**A. 144 min**B. 192 min

C. 81 min

D. 108 minExplanation:

Let the slower pipe alone fill the tank in x min.

Then, faster pipe will fill it in x/3 min.

1/x + 3/x = 1/36

4/x = 1/36 => x = 144 min.