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Quantitative Aptitude

PIPES AND CISTERN MCQs

Pipes & Cisterns

Total Questions : 431 | Page 2 of 44 pages
Question 11.

  1. If two pipes function simultaneously, a reservoir will be filled in 12 hours. One pipe fills the reservoir 10 hours faster than the other. How many hours does the faster pipe take to fill the reservoir?

  1.    10 hr.
  2.    15 hr.
  3.    15 hr.
  4.    20 hr.
 Discuss Question
Answer: Option D. -> 20 hr.
Question 12.

  1. There is a leak in the bottom of a cistern. Before the leak, it could be filled in \(3\frac{1}{2}\)  hours, it now takes \(\frac{1}{2}\) hour longer. If the cistern is full, the time taken to empty the cistern would be

  1.    24 hr.
  2.    28 hr.
  3.    32 hr.
  4.    34 hr.
 Discuss Question
Answer: Option B. -> 28 hr.
Question 13.

  1. A filler pipe can fill  \(\frac{1}{6}^{th}\)  of a cistem in 10 minutes. In how many minutes, can it fill  \(\frac{5}{8}^{th}\) of the cistern?

  1.    37 min.
  2.    37.5 min
  3.    38 min
  4.    38.5 min.
 Discuss Question
Answer: Option B. -> 37.5 min
Question 14.

  1. An outlet pipe can empty \(\frac{2}{3}^{rd}\) of a cistern in 12 minutes. In 8 minutes, what part of the cistern will be emptied?

  1.    \(\frac{2}{3}\)
  2.    \(\frac{3}{2}\)
  3.    \(\frac{4}{9}\)
  4.    \(\frac{9}{4}\)
 Discuss Question
Answer: Option C. -> \(\frac{4}{9}\)
Question 15.

  1. Two pipes can separately fill a tank in 20 hours and 30 hours respectively. Both the pipes are opened to fill the tank but when the tank is full, a leak develops in tl1e tank through which one-third of water supplied by both the pipes goes out. What is the total time taken to fill the tank?

  1.    14 hr.
  2.    15 hr.
  3.    16 hr.
  4.    17 hr.
 Discuss Question
Answer: Option C. -> 16 hr.
Question 16.

  1. Two pipes X and Y can separately fill a cistern in 18 hours and 24 hours respectively. If they are turned on alternately for one hour each, how long will it take to fill the cistern?

  1.    20 hr.
  2.    20 hr. 30 min.
  3.    21 hr. 
  4.    21 hr. 30 min.
 Discuss Question
Answer: Option B. -> 20 hr. 30 min.
Question 17.

  1. Two filler pipes X and Y can separately fill a tank in 45 and 40 minutes respectively. They start to fill the tank together but pipe X is turned off after a few minutes and pipe Y fills the rest of the tank in 23 minutes. After how many minutes is pipe X turned off?

  1.    6 min.
  2.    9 min.
  3.    12 min.
  4.    none of these
 Discuss Question
Answer: Option B. -> 9 min.
Question 18.
  1. One filler pipe is 5 times faster than the other and takes 48 minutes less than the other pipe to fill a tank. In how many minutes would the tank be full if both the pipes are opened?

  1.    7 min.
  2.    8 min.
  3.    9 min.
  4.    10 min.
 Discuss Question
Answer: Option D. -> 10 min.

Let the slower pipe fill the tank in x minutes, then the faster pipe will fill the tank in (x/5) minutes.

According to the given condition, the faster pipe takes 48 minutes less than the slower pipe to fill the tank. So, we have:

x - (x/5) = 48

Simplifying the above equation, we get:

4x/5 = 48

x = 60

Therefore, the slower pipe will fill the tank in 60 minutes and the faster pipe will fill the tank in 12 minutes (x/5 = 60/5 = 12).

Now, to find the time taken by both pipes together to fill the tank, we use the following formula:

Time taken by both pipes together = (Time taken by slower pipe × Time taken by faster pipe) / (Time taken by slower pipe + Time taken by faster pipe)

Substituting the values, we get:

Time taken by both pipes together = (60 × 12) / (60 + 12)

= 720/72

= 10

Therefore, both pipes together will fill the tank in 10 minutes.

Hence, the correct answer is option D, 10 min.

Let's understand the concepts and formulas used in this problem in more detail:

  • Pipes and Cisterns: In the pipes and cisterns problems, we deal with the time taken by pipes or cisterns to fill or empty a tank. We use the formula:

Work done = (Rate of work × Time taken)

  • Rate of work: Rate of work is the amount of work done by a pipe or cistern in one unit of time. We use the formula:

Rate of work = 1 / Time taken

  • Time and Work: In the time and work problems, we deal with the time taken by a person or machine to complete a task. We use the formula:

Work done = (Efficiency × Time taken)

  • Efficiency: Efficiency is the amount of work done by a person or machine in one unit of time. We use the formula:

Efficiency = Work done / Time taken


By using the above concepts and formulas, we have solved the given problem to find the time taken by both pipes together to fill the tank, which is 10 minutes.

Question 19.

  1. Six pipes are fitted to a tank. Some of these are filler pipes and some are outlet pipes. Each filler pipe can fill the tank in 8 hours and each outlet pipe can drain off the water in 12 hours. On opening all the pipes, an empty tank is filled in 3 hours. Find the number of filler pipes.

  1.    2
  2.    3
  3.    4
  4.    5
 Discuss Question
Answer: Option C. -> 4
Question 20.

  1. A tank can be filled by pipes X and Y in \(7\frac{1}{2}\)  hours. Both of them are opened for \(2\frac{1}{2}\) hours and then Y is closed. X alone now requires \(6\frac{2}{3}\) hours more to fill the tank. The time required by X to fill the tank alone will be

  1.    8 hr.
  2.    10 hr.
  3.    12 hr.
  4.    none of these
 Discuss Question
Answer: Option B. -> 10 hr.

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