Quantitative Aptitude

Pipes and Cisterns

535 Questions
All Delayed opening or closing 106 Combined pipes and the LCM shortcut 77 Find unknown pipe time 64 Efficiency ratios and faster-pipe relations 61 Flow rates based on pipe diameter 50 Leaks and reverse-rate questions 50 Actual capacity and pump-rate equations 44 Partial filling or emptying condition 44 Alternating pipes and changing phases 39

Pipes and Cisterns Questions

Multiple choice

DIRECTION for the question: Solve the following question and mark the best possible option. A bath can be filled by the cold water pipe in 10 minutes and by the hot water pipe in 15 minutes. A person leaves the bathroom after turning on both the pipes. He returns just when the bath should have been full. Finding, however, the waste pipe was open, he closes it. In 4 minutes more, the bath is full. In what time will the waste water pipe empty it?

  1. 30 minutes

  2. 15 minutes

  3. 9 minutes

  4. 19 minutes

  5. 10 minutes
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice

Two inlet pipes, A and B, can fill a cistern in 12 hours and 15 hours respectively. A third pipe, C, is an outlet pipe that can empty the cistern in 20 hours. All three pipes are opened together, but after 4 hours, pipe C is closed and another outlet pipe, D, which can empty the cistern in 30 hours, is opened instead. If the cistern was empty at the start, in how much total time will it be completely filled? (approximately in hours)

  1. 7

  2. 9

  3. 12

  4. 15

  5. 16
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Rates (per hour): A=1/12, B=1/15, C=-1/20. Combined rate = 1/12 + 1/15 - 1/20 = (5+4-3)/60 = 6/60 = 1/10. In 4 hours, they fill 4/10 = 2/5 of the cistern. Remaining = 3/5. New rate (C replaced by D): A+B-D = 1/12 + 1/15 - 1/30 = (5+4-2)/60 = 7/60. Time to fill remaining = (3/5) / (7/60) = (3/5) * (60/7) = 36/7 approx 5.14 hours. Total time = 4 + 5.14 = 9.14 hours.

Multiple choice

A tank is fitted with two inlet pipes, P and Q, and one outlet pipe, R. Pipe P can fill the tank in 4 hours, Q can fill it in 6 hours, and R can empty it in 8 hours. If P and Q are opened for 1 hour, and then R is also opened, how much total time will it take to fill the tank?

  1. 2 hours

  2. 3 hours

  3. 4 hours

  4. 5 hours

  5. 6 hours
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

P fills 1/4, Q fills 1/6, R empties 1/8 per hour. In 1 hour, P+Q fill 1/4 + 1/6 = 5/12. Remaining = 7/12. With R open, net rate = 1/4 + 1/6 - 1/8 = (6+4-3)/24 = 7/24. Time to fill remaining = (7/12) / (7/24) = 2 hours. Total time = 1 + 2 = 3 hours.

Multiple choice

A reservoir has an inlet pipe (Pipe P) that can fill the reservoir in 18 hours and an outlet pipe (Pipe R) that can empty it in 30 hours. If the inlet pipe is opened alone for 6 hours and then the outlet pipe is also opened while the inlet pipe continues to run, how much additional time is required to fill the remaining part the reservoir completely?

  1. 15 hours

  2. 22 hours

  3. 24 hours

  4. 30 hours

  5. 34 hours
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Pipe P fills at 1/18 per hour, Pipe R empties at 1/30 per hour. In 6 hours, P fills 6/18 = 1/3 of the reservoir. Remaining 2/3 must be filled by (P-R), which is 1/18 - 1/30 = (5-3)/90 = 2/90 = 1/45 per hour. Time = (2/3) / (1/45) = 30 hours.

Multiple choice

Three pipes A, B and C are connected to a tank. Out ofthe three, A and B are the inlet pipes and C is the outletpipe. If opened separately, A fills the tank in 10 hoursand B fills the tank in 30 hours. If all three are openedsimultaneously, it takes 30 minutes extra than if only Aand B are opened. How much time does it take toempty the tank if only C is opened?

  1. 140 Hours

  2. 100 Hours

  3. 200 Hours

  4. 120 Hours

  5. 160 Hours
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Rate of A = 1/10, Rate of B = 1/30. Combined rate (A+B) = 1/10 + 1/30 = 4/30 = 2/15. Time for A+B = 15/2 = 7.5 hours. Combined rate (A+B-C) = 1/(7.5 + 0.5) = 1/8. So, 2/15 - Rate C = 1/8. Rate C = 2/15 - 1/8 = (16-15)/120 = 1/120. Thus, C empties the tank in 120 hours.

Multiple choice

A water pipe can fill a swimming pool in 12 hours, while another pipe can drain the full pool in 18 hours. If both pipes are opened simultaneously, how long will it take to fill the pool completely?

  1. 24 hours

  2. 36 hours

  3. 48 hours

  4. 72 hours

  5. 108 hours
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The filling pipe fills 1/12 of the pool per hour, and the draining pipe removes 1/18 of the pool per hour. The combined rate is 1/12 - 1/18 = 3/36 - 2/36 = 1/36 of the pool per hour. Thus, it takes 36 hours to fill the pool.

Multiple choice

DIRECTION for the question: Solve thefollowing question and mark the best possibleoption.Two pipes A and B can fill a tank in 15 hoursand 20 hours respectively while a third pipe Ccan empty the full tank in 25 hours. All the threepipes are opened in the beginning. After 10hours, C is closed. In how much time will thetank be full?

  1. 13HRS

  2. 16HRS

  3. 12HRS

  4. 18HRS

  5. 20HRS
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Work rates: A=1/15, B=1/20, C=-1/25. Combined rate = (20+15-12)/300 = 23/300. In 10 hours, work done = 230/300 = 23/30. Remaining work = 7/30. After C closes, rate = 1/15 + 1/20 = 7/60. Time to finish = (7/30) / (7/60) = 2 hours. Total time = 10 + 2 = 12 hours.

Multiple choice

One inlet pipe fills an empty tank in 5 hours. A second inlet pipe fills the same tank in 3 hours. If both pipes are used together, how long will it take to fill 2/3 of the tank?

  1. 8/15 hr

  2. 3/4 hr

  3. 5/4 hr

  4. 15/8 hr

  5. 8/3 hr
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pipe 1 fills 1/5 of the tank per hour, and pipe 2 fills 1/3 of the tank per hour. Together, they fill (1/5 + 1/3) = 8/15 of the tank per hour. To fill 2/3 of the tank, the time required is (2/3) / (8/15) = (2/3) * (15/8) = 5/4 hours.

Multiple choice

Pipe X can fill the reservoir in 20 hours, and pipe Y can fill it in 30 hours. A drain pipe Z can empty the full reservoir in y hours. All three pipes were opened simultaneously at 6:00 a.m, and the drain pipe Z was closed at 12:00 p.m. The reservoir was completely filled by 8:00 p.m. Find the value of y.

  1. 20

  2. 24

  3. 36

  4. 40
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let reservoir capacity = 60 units. Rate X = 3, Rate Y = 2, Rate Z = -60/y. Pipes X, Y, Z open for 6 hours (6am to 12pm): 6 * (3 + 2 - 60/y) = 30 - 360/y. Remaining work = 60 - (30 - 360/y) = 30 + 360/y. Pipes X, Y open for 8 hours (12pm to 8pm): 8 * (3 + 2) = 40. So 30 + 360/y = 40 => 360/y = 10 => y = 36.

Multiple choice

Directions: The question given below is followed by two statements labelled I and II. You have to determine whether the data given in the statements is sufficient for answering the question. You should use the data and your knowledge of Mathematics to choose the best possible answer. How long will leakage take to empty the full tank? (I) Pipe A takes 2 hours to fill half the tank and takes 1 extra hour, if there is a leakage. (II) The cistern has a capacity of 240 litres. Pipe A takes 5 hours to fill the whole tank, if there is a leakage.

  1. The question can be answered by using statement-I alone, but cannot be answered using the other statement alone.

  2. The question can be answered by using statement-II alone, but cannot be answered using the other statement alone.

  3. The question can be answered by using either of the statements alone.

  4. The question can be answered using both the statements together, but cannot be answered using either of the statements alone.

  5. The question cannot be answered even by using both the statements together.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Statement I says Pipe A fills half in 2 hours (full in 4 hours). With leakage, it takes 1 extra hour (5 hours total). Let L be the time for the leak to empty the tank. 1/4 - 1/L = 1/5. This allows solving for L. Statement II provides similar info but is redundant or consistent. Thus, I alone is sufficient.

Multiple choice

Quantity A The time taken to fill a tank using two pipes, one filling at 3 liters per minute and the other at 5 liters per minute, when the tank capacity is 120 liters Quantity B 20 minutes

  1. Quantity A is greater.

  2. Quantity B is greater.

  3. The two quantities are equal.

  4. The relationship cannot be determined from the information given.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Quantity A: Combined rate = 3 + 5 = 8 liters/min. Time = 120 / 8 = 15 minutes. Quantity B = 20 minutes. Since 15 < 20, Quantity B is greater.

Multiple choice

If two pipes are opened simultaneously, they can fill an empty tank in 36 minutes. The first pipe, when operating alone, takes 90 minutes to fill the tank. If the second pipe releases 40 liters more water per minute than the first pipe, what is the total capacity of the tank?

  1. 2,700 liters

  2. 3,600 liters

  3. 6,300 liters

  4. 7,200 liters

  5. 8,100 liters
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Pipe 1 rate = 1/90. Combined rate = 1/36. Pipe 2 rate = 1/36 - 1/90 = (5-2)/180 = 3/180 = 1/60. Pipe 2 is faster by 1/60 - 1/90 = 1/180 per minute. 1/180 of capacity = 40 liters, so capacity = 40 * 180 = 7200.

Multiple choice

Two pipes can fill a tank in 10 minutes together if the efficiency of the first pipe is 8 times the efficiency of the second pipe find the time required to fill the tank using the second pipe alone.

  1. 88 minutes

  2. 87 minutes

  3. 89 minutes

  4. 90 minutes

  5. 93 minutes
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let efficiency of second pipe be x, then first is 8x. Combined efficiency = 9x. Time = 10 mins. Total work = 90x. Time for second pipe = 90x / x = 90 minutes.