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

இரண்டு குழாய்கள் ஒரு தொட்டியை 4 மணி நேரத்திலும் 6 மணி நேரத்திலும் தனித்தனியே நிரப்புகின்றன.ஒரே சமயத்தில் இரு குழாய்களும் திறக்கப்பட்டால் தொட்டி நிரப்புவதற்கு தேவைப்படும் நேரம் என்ன? Two tubes fill a tank separately at 4 hrs. and 6 hrs. What is the time required to fill the tank if both pipes are opened at the same time?

  1. 180 நிமிடங்கள் /180minutes

  2. 148 நிமிடங்கள்/ 148minutes

  3. 164 நிமிடங்கள்/ 164minutes

  4. 144 நிமிடங்கள் /144minutes

  5. இவற்றில் ஏதுமில்லை/None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Pipe 1 rate = 1/4 per hour. Pipe 2 rate = 1/6 per hour. Combined rate = 1/4 + 1/6 = 5/12 per hour. Time to fill = 12/5 hours = 2.4 hours. 2.4 * 60 minutes = 144 minutes.

Multiple choice

Directions: The following questions are accompanied by three statements A, B and C. You have to determine which statement(s) is/are sufficient necessary to answer the questions and mark your answer accordingly. In how many hour 'C' alone can fill the cistern? (A) Ratio of efficiency of A, B and C is 2:4:5 (B) A opened throughout the time, B opened for starting 10 minutes and 'C' opened after 2 minutes of closing of B. A, B and C fill equal amount of water in the cistern. (C) If A and B work alternatively, they can fill the tank in 40 minutes.

  1. Any two of them

  2. Either A and B or B and C

  3. A and B together only

  4. Any one of them

  5. Either B or A and C together
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Statement A provides the ratio of efficiencies, which is insufficient alone. Statement B provides information about the work done by A, B, and C, allowing for the calculation of their individual efficiencies relative to each other. Statement C allows for the calculation of the combined efficiency of A and B. Any two statements provide enough equations to solve for the individual rates and the total capacity.

Multiple choice

A tank connected with 15 pipes, some of them are inlet pipes, and the rest work as outlet pipes. Each of the Inlet pipes can fill the tank in 8 hour individually while each of those that drain the tank can drain it in 6 hours individually. If all the pipes are kept open when the tank is full. It will take exactly 6 hour for the tank to empty. How many of these are Inlet pipes?

  1. 4

  2. 8

  3. 3

  4. 6

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

Let x be the number of inlet pipes. Then 15-x are outlet pipes. The rate of filling is x/8 and the rate of emptying is (15-x)/6. The net rate is -1/6 (since it empties in 6 hours). So, x/8 - (15-x)/6 = -1/6. Multiplying by 24 gives 3x - 4(15-x) = -4, so 3x - 60 + 4x = -4, 7x = 56, x = 8.

Multiple choice

Faucet A basically used as inlet pipe and Faucet B is used as outlet pipe. Faucet A and B both are opened simultaneously, all the time. When Faucet A fills the tank and Faucet B empty the tank, it will take thrice the time than when both the pipes fill the tank. When Faucet B is used for filling the tank, its efficiency remains constant. What is the ratio of efficiency of Faucet A and Faucet B respectively?

  1. 1:2

  2. 2:1

  3. 1:3

  4. 3:1

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice

Two filling pipes A and B together can fill a tank with rate of 40 lit/min and 60 lit/min respectively in 8 min. If a waste pipe can empty the filled tank in 32 min. then what is the rate of waste pipe (in lit/min)

  1. (a) 30 lit/min.

  2. (b) 25 lit/min.

  3. (c) 20 lit/min.

  4. (d) 16 lit/min.

  5. (e) 24 lit/min.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Combined rate of filling = 40 + 60 = 100 lit/min. In 8 min, they fill 800 liters. If a waste pipe empties it in 32 min, its rate is 800 / 32 = 25 lit/min.

Multiple choice

Two pipes A and B together can fill a tank in 20 hours. Ratio of efficiency A and B is 5 : 4. They together filled the tank for the first 4 hours. Then B is closed and another pipe C is opened. Now if tank is filled in another 9 hours then Pipe C alone can fill the tank in how many hours.

  1. 90/7 hour

  2. 80/5 hour

  3. 180/11 hour

  4. 180/7 hour

  5. 90/11 hour
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Efficiency ratio A:B = 5:4. Let A=5k, B=4k. Together they fill 1/20 of the tank per hour. 9k = 1/20, so k = 1/180. A=5/180, B=4/180. In 4 hours, they fill 4 * (9/180) = 36/180 = 1/5. Remaining tank = 4/5. Pipe B is closed, C is opened. A+C fill 4/5 in 9 hours, so A+C = (4/5)/9 = 4/45. Since A=1/36, C = 4/45 - 1/36 = (16-5)/180 = 11/180. C fills the tank in 180/11 hours.

Multiple choice

A tank of 425 litres capacity has been filled with water through two pipes, the first pipe having been opened five hours longer than the second. If the first pipe were open as long as the second, and the second pipe was open as long as the first pipe was open, then the first pipe would deliver half the amount of water delivered by the second pipe; if the two pipes were open simultaneously, the tank would be filled up in 17 hours. How long was the second pipe open?

  1. 10 hours

  2. 12 hours

  3. 15 hours

  4. 18 hours
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let t1 and t2 be the times. t1 = t2 + 5. Rates r1, r2. 425 = r1*t1 + r2*t2. Also, r1/r2 = (r2*t2)/(r1*t1) = 1/2. This leads to a system of equations. Solving gives t2 = 15.

Multiple choice

In the ancient city of Portheus, the emperor has installed an overhead tank that is filled by two pumps - X and Y. X can fill the tank in 12 hours while Y can fill the tank in 15 hours. There is a pipe Z which can empty the tank in 10 hours. Both the pumps are opened simultaneously. The supervisor of the tank, before going out on a work, asks his assistant to open Z when the tank is exactly 40% filled so that tank is exactly filled up by the time he is back. If he starts X and Y at exactly 11:00 AM and he comes back atA:B. Then find the value of A+ B.

  1. 30

  2. 41

  3. 47

  4. 50
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice

Two pipes A and B can fill up a half full tank in 1.2 hours. The tank was initially empty. Pipe B was kept open for half the time required by pipe A to fill the tank by itself. Then, pipe A was kept open for as much time as was required by pipe B to fill up 1/3 of the tank by itself. It was then found that the tank was 5/6 full. The least time in which any of the pipes can fill the tank fully is

  1. 4.8 hours

  2. 4 hours

  3. 3.6 hours

  4. 6 hours
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let A and B fill the tank in a and b hours. 1/2(1/a + 1/b) = 1/1.2 = 5/6, so 1/a + 1/b = 5/3. Pipe B runs for a/2, Pipe A runs for b/3. (a/2)/b + (b/3)/a = 5/6. Let x = a/b. (1/2)x + (1/3)(1/x) = 5/6. 3x^2 - 5x + 2 = 0. (3x-2)(x-1) = 0. x = 2/3 or 1. Solving leads to 4 hours.

Multiple choice

Three pipes A, B, C can fill an empty cistern in 2, 3 and 6 hours, respectively. They are opened together. After what time should B be closed, so that the cistern gets filled in exactly 1 hr 15 min?

  1. 30 min

  2. 20 min

  3. 45 min

  4. 15 min
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A, B, C fill 1/2, 1/3, 1/6 per hour. Combined rate = 1/2 + 1/3 + 1/6 = 1. Total time = 1.25 hours. If B is closed after t hours, (1/2 + 1/6)*1.25 + (1/3)*t = 1. (2/3)*1.25 + t/3 = 1. 0.833 + t/3 = 1. t/3 = 0.166. t = 0.5 hours = 30 min.

Multiple choice

A water tank can be filled by pipes P and Q in 4 minutes and 3 minutes, respectively. When the tank is full, it can be emptied by opening a hole in 2 minutes only. If all the taps are turned on at the same time, then the water tank will be filled in

  1. 12 minutes

  2. 6 minutes

  3. 24 minutes

  4. 48 minutes

  5. 1/12 minutes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

P fills 1/4 tank per minute, Q fills 1/3 tank per minute, and the hole empties 1/2 tank per minute. The net rate is (1/4 + 1/3 - 1/2) = (3/12 + 4/12 - 6/12) = 1/12 tank per minute. Thus, the tank fills in 12 minutes.

Multiple choice

The ratio of the rate of filling of two pipes X and Y is 2:1,respectively. If together they can fill 4/5th of tank in 16minutes, then find the time taken by pipe X alone to fill thetank completely.

  1. 30 minutes

  2. 20 minutes

  3. 36 minutes

  4. 25 minutes

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let rates be 2r and r. Combined rate = 3r. 3r * 16 = 4/5 * Tank. So, 48r = 0.8 * Tank, meaning 1 Tank = 60r. Pipe X rate = 2r. Time for X = 60r / 2r = 30 minutes.