Top 130 Pipe and cistern questions for Competitive Exams [ 100% FREE ]

Introducing an important aspect of the quantitative aptitude section: the Pipe and cistern questions. A common challenge candidates face in various competitive exams, be it banks, SSC, RRB, Insurance and more, is problems related to pipes and cisterns. In this comprehensive article, we delve deep into “Pipe and cistern questions“, ensuring you get the most effective preparation material.

For many, the term “Pipe and cistern questions” can seem daunting, but with the right approach and understanding of the “pipes and cisterns formula“, it becomes manageable. This is why we’re emphasizing on the crucial examples like “two pipes p and q together can fill a cistern” and “two pipes a and b can fill a cistern“. Both these examples will give you a clear perspective on how to approach these problems.

We also recognize the importance of language adaptability in preparation. Therefore, we have also incorporated “pipe and cistern questions in Hindi” and insights on “pipe and cistern in Hindi“. This ensures that you not only understand the crux of the “pipes and cisterns problems” but also can relate to them in a language you’re comfortable with.

Word problems, especially around the “pipes and cisterns formula“, have been a mainstay in competitive exams. While “two pipes p and q together can fill a cistern” or “two pipes a and b can fill a cistern” might seem similar, they can carry nuances that are essential for aspirants to grasp.

Pipes and Cisterns Formula :

Given below are aimportant formulas which shall help you solve the pipes and cistern based questions quicker and more efficiently:

  • If x hours are required to fill up a tank, then part filled in 1 hr =1/x
  • If y hours are required to empty the tank, then part emptied in 1 hour = 1/y
  • If a pipe can fill a tank in x hours and can empty the same tank in y hours. When both the pipes are opened at the same time, then the net part of the tank filled in 1 hr = {(xy) / (y-x)}, provided y>x
  • If a pipe can fill a tank in x hours and can empty the same tank in y hours. When both the pipes are opened at the same time, then the net part of the tank filled in 1 hr = {(xy) / (x-y)}, provided x>y
  • Net work done = (Sum of work done by Inlets) – (Sum of work done by Outlets)
  • One inlet can fill the tank in x hr and the other inlet can fill the same tank in y hrs, if both the inlets are opened at the same time, the time taken to fill the whole tank = {(xy) / (y+x)}
  • If two pipes take x and y hours respectively to fill a tank of water and a third pipe is opened which takes z hours to empty the tank, then the time taken to fill the tank = {1 / (1/x)+(1/y)+(1/z)} and the net part of the tank filled in 1 hr = (1/x)+(1/y)-(1/z)

The syllabus for competitive exams is vast, as we all know. But every topic, including “Pipe and cistern questions“, holds its weight. Therefore, giving due time to understand and practice these “pipes and cisterns problems” is paramount. Especially when considering the intense competition and the challenge to crack these exams.

In conclusion, this article offers an in-depth understanding of “Pipe and cistern questions“, covering essential examples like “two pipes p and q together can fill a cistern” and “two pipes a and b can fill a cistern“, not forgetting the importance of language with “pipe and cistern questions in Hindi” and “pipe and cistern in Hindi“.

Whether you’re just starting out or brushing up your skills, this article is your guide to excel. So, gear up and dive into the world of “Pipe and cistern questions” and ace your upcoming Government sector exams!

Top 130 Pipe and cistern questions for Competitive Exams :

21. Pipe A and B are inlet pipe. Pipe A alone can fill the tank in 9 hours while the efficiency of pipe B is 50% more than that of A. Pipe C alone can empty the same tank in 12 hours. If all the pipes opened together then in how many hours will 2/3rd of tank be filled?

पाइप A और B इनलेट पाइप हैं। पाइप A अकेले टंकी को 9 घंटे में भर सकता है जबकि  पाइप B की कार्य कुशलता A से 50% अधिक है। पाइप C वही टंकी को अकेले 12 घंटे में खाली कर सकता है। यदि सभी पाइपों को एक साथ खोला जाता है तो कितने घंटे में टंकी का 2/3 हिस्सा भर जाएगा?


Option “C” is correct.

⇒ Pipe A alone can fill the tank in = 9 hours

⇒ Efficiency of pipe B = 1/9 × 150/100 = 1/6 hours

⇒ Pipe C alone can empty the tank in 12 hours

⇒ Efficiency of pipe A, B and C = 1/9 : 1/6 : 1/12 = 4 : 6 : 3

⇒ Total work = LCM of 9,6, and 12 is 36.

⇒ 2/3rd of total work = 36 × 2/3 = 24

⇒ A, B and C together will complete the 2/3rd of the total work in = 24/(4 + 6 – 3) = 24/7 hours

22. Three pipes A, B and C empty in a tank. A and B fill the tank in 5 and 10 minutes respectively when operated separately and C empties the tank in 4 minutes. When all three pipes are operated together, 200 litres of water is poured into the tank in one minute. What is the capacity of the tank?

एक टैंक में तीन पाइप A, B और C खाली किये जाते हैं। जब अलग से संचालित किये जाते हैं तो A और B टैंक को क्रमशः 5 और 10 मिनट में भरते हैं और C टैंक को 4 मिनट में खाली कर देता है। जब तीनों पाइप एक साथ संचालित होते हैं, तो एक मिनट में 200 लीटर पानी टैंक में डाला जाता है। टैंक की क्षमता क्या है?


Option “D” is correct.

 The work done by three pipes in one minute when operated separately, 

A = 1/5, B = 1/10, C = -1/4

When operated together, the amount of work done in one minute = 1/5 + 1/10 – 1/4

⇒ (4 + 2 – 5)/20 = 1/20

⇒ 1/20th of the work is done in one minute.

⇒ 1 min = (1/20th) work

⇒ 20 min = 1 work

Total work is done in 20 minutes when all three pipes are operated.

In one minute, 200 litres of water is poured, 

So, the capacity of tank = 20 × 200 = 4000 litres

∴ The capacity of the tank is 4000 litres.

23. Taps P, Q, and R can fill a tank in 20, 25, and 40 hours respectively. Taps Q is kept open for 10 hours, and then tap Q is closed, after that tap P and R are opened. Tap R is closed 9 hours before the tank overflows. How long does it take to fill the tank?

नल P, Q और R एक टंकी को क्रमशः 20, 25 और 40 घंटों में भर सकते हैं नल Q को 10 घंटे के लिए खोला जाता है, और फिर नल Q को बंद किया जाता है और नल P और R को खोला जाता है। नल R को टंकी भरने से 9 घंटे पहले बंद कर दिया जाता है। टंकी भरने में कितना समय लगता है?


Option “B” is correct.

Given:

Tap P can fill a tank = 20 hours

Tap Q can fill a tank = 25 hours

Tap R can fill a tank = 40 hours

Calculation:

Let the total work be LCM of 20, 25, and 40 = 200 units

⇒ Efficiency of tap P = 200/20 = 10 units

⇒ Efficiency of tap Q = 200/25 = 8 units

⇒ Efficiency of tap R = 200/40 = 5 units

Since the tap Q is kept open for 10 hours,

Work done by tap Q = 10 × 8 = 80 units

∵ Tap R is closed 9 hours before the tank overflows

⇒ Tap P alone worked for 9 hours.

⇒ Work done by tap P alone = 9 × 10 = 90 units

Remaining work = 200 – (80 + 90) = 30 units

The remaining work was done by tap P and tap R together

Time taken by tap P and Tap R to complete the remaining work = 30/(10 + 5) = 30/15 = 2 hours

∴ The total time to fill the tank is (10 + 9 + 2) 21 hours.

24. Pipes A and B can empty a full tank in 8 and 12 hours, respectively. C is a filling pipe. All the three pipes were opened together at the same time and one-sixth of the tank got emptied in one hour. C alone can fill the tank in:

पाइप A और B क्रमशः 8 और 12 घंटे में एक पूर्ण टैंक खाली कर सकते हैं। C एक भरने वाला पाइप है। तीनों पाइप एक साथ एक ही समय में खोले गए और एक घंटे में टैंक का छठा हिस्सा खाली हो गया। C अकेले टैंक को कितने समय में भर सकता है:


Option “C” is correct.

Given:

Pipes A and B can empty a full tank in 8 and 12 hours, respectively.

C is a filling pipe.

All the three pipes were opened together at the same time and one-sixth of the tank got emptied in one hour.

Formula:

If a pipe empties a tank in ‘a’ hours and an another empties the same tank in ‘b’ hours then

Total work = LCM of the times taken by two different pipes = LCM of (a, b)

Efficiency of first pipe = (-) LCM of (a, b)/a

Efficiency of second pipe = (-) LCM of (a, b)/b

Time taken to fill the tank = Total work/The combined efficiency of the pipes.

Now if another pipe fills the tank in ‘c’ hours, then

Combined efficiency of the three pipes = (- efficiency of pipe A) + (- efficiency of pipe B) + (+ efficiency of pipe C)

(-)ve sign is mentioned as they empty the tank and (+)ve sign is to imply that the pipe fills the tank.

Calculation:

Here in the fig, LCM of (8, 12) = 24 = Total work 

Efficiency of A = 24/8 = 3

Efficiency of B = 24/12 = 2

(-)ve sign is mentioned as A and B empty the tank.

1/6th of total work = 24/6 = 4 = combined efficiency of three pipes

Let the efficiency of pipe C be x, then

⇒ x – 3 – 2 = – 4

⇒ x = 5 – 4

⇒ x = 1

∴ the pipe C alone can fill the tank in = 24/1 = 24 hrs

25. Pipes A and B can fill a tank in 10 hours and 40 hours respectively. C is an outlet pipe attached to the tank. If all the three pipes are opened simultaneously, it takes 80 minutes more time than  A and B together takes to fill the tank. If A and B kept open for 7 hours and closed and then C opened. How much time will C take to empty the tank :

पाइप A और B क्रमशः 10 घंटे और 40 घंटे में एक टंकी को भर सकते हैं। C एक निर्गम पाइप है जो टंकी से जुड़ी है। यदि सभी तीन पाइप एक साथ खोले जाते हैं, तो A और B मिलकर टंकी को भरने में जितना समय लेते है उससे 80 मिनट अधिक समय लगता है A और B को 7 घंटे खुला रखा जाता है और फिर बंद कर दिया जाता है और C को खोल दिया जाता है। अब C टंकी को खाली कर देगा:


Option “A” is correct.

Total work = 40

Time taken to fill the tank A and B together = 40/(1 + 4) = 8 hrs

Let the efficiency of C be x.

If all three pipe A, B and outlet pipe C open, time taken to fill the tank = 8 hr + 80 min = 9 + 1/3 = 28/3 hrs

Efficiency of A,  B and C = 40/(28/3) = 30/7

According to the question

4 + 1 + x = 30/7

⇒ x = 30/7 – 5

⇒ x = (–5/7)

Work done by A and B in 7 hrs = (4 + 1) × 7 = 35

∴ Pipe C empty the tank filled by A and B in 7 hrs = 35/(5/7) = 49 hrs

26.Select the correct alternative from the given choices.

Tap A can fill a cistern in 12 hours and tap B can fill the same cistern in 8 hours while tap C can empty full cistern in 10 hours. Tap A started at 9 a.m. and tap B started at 11 a.m. At what time tap C should be started such that the cistern will be half full at 1 pm?

दिए गए विकल्पों में से सही विकल्प का चयन कीजिए।

नल A, 12 घंटे में एक सिस्टर्न भर सकता है और B उसी सिस्टर्न को 8 घंटे में भर सकता है जबकि नल C, 10 घंटे में पूरा सिस्टर्न खाली कर सकता है। नल A सुबह 9 बजे शुरू हुआ और नल B, सुबह 11 बजे शुरू हुआ। किस समय C नल को शुरू किया जाना चाहिए कि दोपहर 1 बजे सिस्टर्न आधा भर जाए?


Option “A” is correct.

Let the capacity of the cistern be 120 litres (LCM of 12, 8 and 10)

Then, in one-hour A fill 10 litres, B fill 15 litres and C empties 12 litres.

Till 1 pm, A filled for four hours and B filled for two hours.

⇒ A filled (4 × 10) = 40 litres

⇒ B filled (2 × 15) = 30 litres

i.e. (40 + 30) = 70 litres filled by 1 pm.

⇒ C should have emptied 10 litres by 1 pm so that the cistern remains half full.

⇒ C will empty 10 litres in 50 minutes

∴ C should be started at 12:10 pm. 

27.Two pipes A and B can fill a tank in 6 hours and 9 hours respectively. They are opened alternately for 1 hour each starting with pipe A first. In how many hours the tank will be filled?

दो पाइप A और B क्रमशः 6 घंटे और 9 घंटे में एक टैंक भर सकते हैं। उन्हें बारी-बारी से पाइप A के साथ शुरू होने वाले प्रत्येक 1 घंटे के लिए खोला जाता है। कितने घंटे में टैंक भर जाएगा?


Option “D” is correct.

Capacity of the tank = LCM of the time taken by A and B.

Capacity of the tank = 18 units

A’s efficiency = 18/6 = 3 units per hour

B’s efficiency = 18/9 = 2 units per hour

2 hours work for A and B = (3 + 2) = 5 units

⇒ 2 × 3 hours = 3 × 5 or 15 units

⇒ 6 hours = 15 units

⇒ 7 hours = 18 units. (At last A fills remaining 3 units)

∴ Tank will be filled in 7 hours.

28. Pipes A and B can fill a tank in 8 hours and 12 hours, respectively whereas pipe C can empty the full tank in 6 hours. A and B are opened for 3 hours and then closed and C is opened instantly. C will empty the tank in:

पाइप A और B एक टंकी को क्रमशः 8 घंटे और 12 घंटे में भर सकते हैं। जबकि पाइप C भरी हुई टंकी को 6 घंटे में खाली कर सकती है। A और B को 3 घंटे के लिए खोला जाता है और फिर बंद कर दिया जाता है और तत्काल C को खोला जाता है। तो C टंकी को कितने घंटे में खाली करेगी?


Option “B” is correct.

Taking LCM of the time taken by 3 pipes for filling and one emptying the tank.

LCM = 24 units    (Total capacity of the tank)

Efficiency of A = 24/8 = 3 units per hour.  (∵ efficiency = work/time)

Efficiency of B = 24/12 = 2 units per hour.

Efficiency of C = 24/6 = 4 units per hour.

(A + B) opened for 3 hours together.

work done by them in 3 hours = (3 + 2) × 3 = 15 units (∵ efficiency = work/time)

Now C has to empty = 15 units (∵ tank in only 15 unis filled by A and B)

Time taken by C to empty this tank = 15/4 = 3(3/4) hours. units (∵ efficiency = work/time)

29. Pipe first can fill a tank in 12 hours and pipe second can fill tank in 15 hours. Both the pipes are opened alternatively for an hour and start with pipe second, but after 4 hours, pipe first is closed. How many hours will be taken to fill the tank?

पहला पाइप एक टैंक को 12 घंटे में भर सकता है और दूसरा पाइप टैंक को 15 घंटे में भर सकता है। दोनों पाइपों को बारी-बारी से (एक घंटे) खोला जाता है और दूसरे पाइप के साथ शुरू किया जाता है, लेकिन 4 घंटे बाद, पहले पाइप को बंद कर दिया जाता है। टैंक को भरने में कितने घंटे लगेंगे?


Option “C” is correct.

Given:

First pipe can fill a tank in 12 hours

Second pipe can fill a tank in 15 hours

Calculation:

First pipe = 12 hours

Second pipe = 15 hours

⇒ Let the total units be 60 (L.C.M. of 12 and 15)

⇒ Now the efficiency of first pipe = 60/12 = 5 units

⇒ The efficiency of second pipe = 60/15 = 4 units

⇒ For 1st hour filled by second pipe = 4 units

⇒ For 2nd hour filled by first pipe = 5 units

⇒ For 3rd hour filled by second pipe = 4 units

⇒ For 4nd hour filled by first pipe = 5 units

⇒ Number of unites done by first and second pipes in 4 hours = 5 + 4 + 5 + 4 = 18 units

⇒ Remaining unites done by second pipe = (60 – 18)/4 = 42/4 = 10.5 hours

∴ To fill the complete tank = 4 + 10.5 = 14.5 hours

30. A tank is filled in 4 hours by three pipes A, B and C. The pipe C is twice as fast as B and pipe B is thrice as fast as A. How much time will pipe A alone take to fill the tank?

एक टंकी तीन पाइप A, B और C द्वारा 4 घंटे में भरा जाता है। पाइप C, पाइप B से दो गुना तेज़ है और पाइप B, पाइप A से तीन गुना तेज़ है। पाइप A को अकेले टंकी को भरने में कितना समय लगेगा?  


Option “B” is correct.

Calculation:

Let the efficiency of pipe A be 1 unit/hour

Efficiency of pipe B = 3 units/hour

Efficiency of C = 6 units/hour

Total efficiency of A, B, and C = 1 + 3 + 6 = 10

They finish in 4 days

⇒ Total work = (1 + 3 + 6) × 4 = 40 units

Pipe A alone can fill the whole tank in = 40/1 = 40 hrs.

∴ The correct answer is 40 hours.

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