Pipes A and B can fill a tank in 40 minutes and 60 minutes. Both are opened for 12 minutes and then A is closed. How many more minutes will B take to fill the tank?
Correct answer C. 30 minutes
Topic / 57 questions
Pipes and Cistern MCQs
Pipes and Cistern MCQs test how quickly pipes fill or empty a tank when they work alone or together, a close cousin of time and work problems. They help aptitude test candidates master rate-based reasoning, and each question shows its correct answer immediately so you can confirm your method.
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Water flows at 9 km/h through a pipe with a cross-sectional area of 0.05 square metres into a rectangular tank 20 m long and 15 m wide. By how many centimetres will the water level rise in 40 minutes?
Correct answer C. 100 cm
Pipes A and B fill a tank in 30 minutes and 20 minutes; pipe C empties it in 60 minutes. A and B are opened on an empty tank, and C is opened 6 minutes later. What is the total time to fill the tank?
Correct answer B. 13.5 minutes
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Pipes A and B together fill a tank in 10 hours, B and C in 12 hours, and C and A in 15 hours. How long would A alone take?
Correct answer C. 24 hours
Pipes A and B fill a tank in 12 hours, B and C in 15 hours, and A and C in 20 hours. How long would A, B and C together take?
Correct answer B. 10 hours
A tank is 2/5 full. Pipe A can fill the whole tank in 10 minutes and pipe B can empty it in 6 minutes. If both are opened, how long will the tank take to empty?
Correct answer D. 6 minutes
Pipe A fills a tank in 6 hours and pipe B empties it in 8 hours. Both are opened on an empty tank, and after 12 hours B is closed. What is the total time taken to fill the tank?
Correct answer B. 15 hours
One pipe fills a tank 12 hours faster than another. Together they fill it in 8 hours. How long does the faster pipe take alone?
Correct answer D. 12 hours
Pipes A and B can fill a tank in 6 hours and 9 hours respectively. They are opened alternately for one hour each, starting with A. In how many hours will the empty tank be full?
Correct answer C. 7 hours
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A 600-litre tank has two inlets delivering 12 and 8 litres per minute and an outlet C. With all three open, the empty tank fills in 50 minutes. How long would C alone take to empty the full tank?
Correct answer C. 75 minutes
Pipes A and B can fill a tank in 20 and 30 minutes respectively. Both are opened together, but A is turned off 5 minutes before the tank is full. How long does the tank take to fill?
Correct answer A. 15 minutes
Pipes A, B and C together fill a tank in 4 hours. A alone takes 12 hours and B alone 15 hours. How long would C alone take?
Correct answer C. 10 hours
Pipe A fills a tank in 15 minutes. When outlet B is also open, the tank takes 40 minutes to fill. How long would B take to empty the full tank?
Correct answer C. 24 minutes
Two taps can fill a tub in 30 minutes and 45 minutes. If both are turned on together, what fraction of the tub is filled in 6 minutes?
Correct answer B. 1/3
A pipe fills 2/3 of a tank in 16 minutes. How much longer will it take to fill the rest of the tank?
Correct answer B. 8 minutes
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A cistern is normally filled in 5 hours, but a leak in its bottom makes it take 30 minutes longer. If the cistern is full, how long will the leak take to empty it?
Correct answer A. 55 hours
Pipes A and B can fill a tank in 10 hours and 12 hours, while pipe C can empty it in 20 hours. If all three are opened on an empty tank, how long will it take to fill?
Correct answer C. 7 hours 30 minutes
A tank is half full. Pipe A can fill the whole tank in 16 hours and pipe B can empty it in 24 hours. If both are opened, in how many hours will the tank be full?
Correct answer D. 24 hours
Four identical taps fill a tank in 9 hours. How long would six such taps take?
Correct answer C. 6 hours
Three identical pipes fill a tank in 12 hours. After 4 hours one pipe is closed. What is the total time taken to fill the tank?
Correct answer C. 16 hours
About Pipes and Cistern MCQs
This topic treats each pipe as doing a fraction of the job per unit of time. Questions ask how long two pipes take to fill a cistern together, how a waste pipe or leak changes the time, and how long a tank takes to empty when an inlet and outlet are open at once. You will also see three-pipe problems where one pipe empties while two fill, and questions where pipes are opened or closed partway through. The key idea is to add filling rates and subtract emptying rates, then take the reciprocal of the total to get the time.
Exams that include Pipes and Cistern MCQs
Pakistan
- NTS
- FPSC
- PPSC
- OTS
- Army/Navy/PAF initial tests
India
- SSC CGL
- SSC CHSL
- IBPS PO
- RRB NTPC
Bangladesh
- Bank job exams
- BCS
- Government job tests
Frequently asked questions
How do you solve a two-pipe filling problem?
Write each pipe's work as a fraction of the tank per minute, add the fractions, and take the reciprocal. For pipes that fill a tank in 15 and 20 minutes, the combined rate is 1/15 plus 1/20, which is 7/60, so together they fill it in 60/7, or about 8.57 minutes.
How do you handle an emptying pipe in these questions?
Treat an emptying or waste pipe as negative work. Subtract its rate from the sum of the filling rates. If the result is positive, the tank fills; if negative, it empties. For example, a filling rate of 1/10 and an emptying rate of 1/15 give a net rate of 1/30 per hour.
Last reviewed October 2026