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Quantitative Aptitude

PIPES AND CISTERN MCQs

Pipes & Cisterns

Total Questions : 431 | Page 1 of 44 pages
Question 1.

  1. To fill a cistern pipes A, B and C take 20 minutes, 15 minutes and 12 minutes respectively. The time, in minutes, that the three pipes together will take to till the cistern is

  1.    5
  2.    7
  3.    9
  4.    12
 Discuss Question
Answer: Option A. -> 5
Question 2.

  1. Two pipes X and Y can fill a cistern in 20 minutes and 30 minutes respectively. A third pipe Z can empty it in 40 minutes. How long would it take to fill the cistern if all the three pipes are opened at the same time?

  1.    \(13\frac{1}{3}\)min
  2.    \(15\frac{1}{5}\)  min.
  3.     \(17\frac{1}{7}\) min.
  4.    none of these
 Discuss Question
Answer: Option C. ->  \(17\frac{1}{7}\) min.
Question 3.

  1. A tap can fill a tank in 16 minutes and another can empty it in 8 minutes. If the tank is already  full and both the taps are opened together will the tank be filled or emptied? How long will it take before the tank is either filled completely or emptied completely as the case may be?

  1.    Empties  , 6 min.
  2.    Filled , 6 min
  3.    Empties  , 8 min.
  4.    Filled , 6 min
 Discuss Question
Answer: Option C. -> Empties  , 8 min.
Question 4.

  1. Two pipes A and B can separately till a tank in 12 minutes and 15 minutes respectively and a third pipe C can drain off 45 litres of water per minute. If all the pipes are opened, the tank can be filled in 15 minutes. What is the capacity of the tank?

  1.    460 liters
  2.    500 liters
  3.    540 liters
  4.    580 liters
 Discuss Question
Answer: Option C. -> 540 liters
Question 5.

  1. An empty cistern has three pipes A, B and C. A and B can fill it in 5 hours and 6 hours respectively and C can empty it in 2 hours. If these pipes are opened in order at 1 a.m., 2 a.m. and 3 a.m., when will the cistern be empty again?

  1.    \(3\frac{1}{2}\) hr. after 3 am
  2.     \(3\frac{1}{4}\)  hr. after 3 am
  3.    \(3\frac{2}{3}\)  hr. after 3 am
  4.     \(3\frac{3}{2}\) hr. after 3 am
 Discuss Question
Answer: Option B. ->  \(3\frac{1}{4}\)  hr. after 3 am
Question 6.

  1. Two pipes A and B can separately fill a tank in 12 minutes and 15 minutes respectively. Both the pipes are opened together but 4 minutes after the start the pipe A is turned off. How much time will it take to fill the tank?

  1.    8 min.
  2.    10 min.
  3.    12 min.
  4.    none of these
 Discuss Question
Answer: Option B. -> 10 min.
Question 7.
  1. Two pipes A and B can separately fill a cistern in 10 minutes and 15 minutes respectively. A person opens both the pipes together. When the cistern should have been full he finds the waste pipe open. He then closes the waste pipe and in another 4 minutes the cistern was full. In what time can the waste pipe empty the cistern when full?

  1.    7 min.
  2.    9 min.
  3.    11 min
  4.    none of these
 Discuss Question
Answer: Option B. -> 9 min.
Let the capacity of the cistern be C, the rate of pipe A be R1, and the rate of pipe B be R2.From the given information, we have:R1 = C/10 (since pipe A can fill the cistern in 10 minutes)R2 = C/15 (since pipe B can fill the cistern in 15 minutes)Let the rate of the waste pipe be R3 (in units of the cistern per minute).When all three pipes are open, the effective rate of filling the cistern is (R1 + R2 - R3) (in units of the cistern per minute).When the waste pipe is open, the effective rate of emptying the cistern is R3 (in units of the cistern per minute).When the waste pipe is closed, the effective rate of filling the cistern is (R1 + R2) (in units of the cistern per minute).
Using the above information, we can write the following equations:C = (R1 + R2 - R3) * t1 (since the cistern should have been full, but due to the waste pipe, it took t1 minutes to fill)C = (R1 + R2) * t2 (since the waste pipe was closed and it took t2 minutes to fill)C = R3 * t3 (since the waste pipe can empty the cistern, it takes t3 minutes to empty it)
We are given that t1 = t2 + 4 (since it took an additional 4 minutes to fill the cistern after the waste pipe was closed)Substituting the above equations, we get:(R1 + R2 - R3) * (t2 + 4) = (R1 + R2) * t2R1 + R2 - R3 = R1 + R2 - (C/t3)R3 = C/t3
Solving the above equations, we get t3 = 9 minutes.
Therefore, the correct option is B. 9 minutes.If you think the solution is wrong then please provide your own solution below in the comments section .
Question 8.

  1. A leak in the bottom of a tank can empty the full tank in 6 hours. An inlet pipe fills water at the rate of 4 litres per minute. When the tank is full, the inlet is opened and due to the leak the tank is emptied in 8 hours. The capacity of the tank is

  1.    5660
  2.    5760
  3.    7560
  4.    6560
 Discuss Question
Answer: Option B. -> 5760
Question 9.

A pipe can fill a cistern in 12 minutes and another pipe can till it in 15 minutes. But a third pipe can empty it in 6 minutes. The first two pipes are kept open for 5 minutes in the beginning and then the third pipe is also opened. In what time is the cistern emptied?


 

  1.    35 min.
  2.    40 min.
  3.    45 min.
  4.    50 min.
 Discuss Question
Answer: Option C. -> 45 min.
Question 10.

  1. A tap can fill a cistern in 6 hours, but due to a leakage at the bottom of the cistern, it takes 1  hours more to fill it. If the cistern is full and the tap is turned off, in what time will the leakage empty the cistern?

  1.    30 hr.
  2.    32 hr.
  3.    34 hr.
  4.    36 hr.
 Discuss Question
Answer: Option A. -> 30 hr.

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