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 general knowledge

Pipe A can fill in 20 minutes and Pipe B in 30 mins and Pipe C can empty the same in 40 mins.If all of them work together, find the time taken to fill the tank

  1. 17 1/7 mins

  2. 20 mins

  3. 8 mins

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Combined rate = 1/20 + 1/30 - 1/40 = (6+4-3)/120 = 7/120 tank per minute. Time to fill = 120/7 = 17 1/7 minutes. Pipe A fills at 5% per minute, B at 3.33%, while C empties at 2.5% per minute, giving a net fill rate of about 5.83% per minute.

Multiple choice general knowledge math & puzzles

A tank has four pipes attached to it. The first one takes 60 hours to fill the tank, second one takes 80 hours to do the same, third one takes 40 hours to empty the tank and the fourth one takes 720 hours to empty the tank. Four taps are opened at the same time. How long will it take to fill the tank if the tank is half-filled before opening the taps?

  1. 7 Days and 12 Hours

  2. 7 Days and 10 Hours

  3. 7 Days and 11 Hours

  4. 7 Days and 13 Hours
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Combined rate: 1/60 + 1/80 - 1/40 - 1/720 = (12+9-18-1)/720 = 2/720 = 1/360 per hour. Half tank needs 0.5 tank at 1/360 rate = 180 hours = 7 days 12 hours. The fill pipes (1,2) together are faster than drain pipes (3,4), so net effect is filling.

Multiple choice general knowledge math & puzzles

A large water tank has two inlet pipes (a large one and a small one) and one outlet pipe. It takes 2 hours to fill the tank with the large inlet pipe. On the other hand, it takes 4 hours to fill the tank with the small inlet pipe. The outlet pipe allows the full tank to be emptied in 6 hours. What fraction of the tank (initially empty) will be filled in 0.86 hours if all three pipes are in operation?

  1. 0.25

  2. 0.45

  3. 0.5

  4. 0.55

  5. 0.75
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Large inlet fills 1/2 tank per hour, small inlet fills 1/4 tank per hour, outlet empties 1/6 tank per hour. Net rate = 1/2 + 1/4 - 1/6 = 6/12 + 3/12 - 2/12 = 7/12 tank per hour. In 0.86 hours: 7/12 * 0.86 = 0.5017, approximately 0.5.

Multiple choice general knowledge math & puzzles

Two pipes A and B can fill a tank in 36 hours and 45 hours respectively. If both the pipes are opened simultaneously, how much time will be taken to fill the tank?

  1. 20 hrs

  2. 40 hrs

  3. 10 hrs

  4. 30 hrs
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Both pipes fill the tank: A at 1/36 per hour and B at 1/45 per hour. Combined rate = 1/36 + 1/45 = (5+4)/180 = 9/180 = 1/20 per hour, so the tank fills in 20 hours. The other options do not match the combined rate.

Multiple choice general knowledge math & puzzles

One pipe can fill a tank three times as fast as another pipe. If together the two pipes can fill the tank in 36 minutes, then the slower pipe alone will be able to fill the tank in:

  1. 81 min

  2. 108 min

  3. 144 min

  4. 192 min
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let the slower pipe's rate be x. The faster pipe's rate is 3x. Combined rate is 4x. In 36 minutes, they fill 4x * 36 = 144x units. The slower pipe alone takes (144x / x) = 144 minutes.

Multiple choice general knowledge math & puzzles

Pipe A can fill a tank in 'a' hours. On account of a leak at the bottom of the tank it takes thrice as long to fill the tank. How long will the leak at the bottom of the tank take to empty a full tank, when pipe A is kept closed?

  1. (2/3)a hours

  2. (3/2)a hours

  3. 3/4)a hours

  4. (5/3) a hours
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Pipe A fills in a hours, so rate = 1/a tank per hour. With the leak, effective rate = 1/(3a). Let leak rate = -1/x (negative because it empties). Then 1/a - 1/x = 1/(3a). Solving: 1/x = 1/a - 1/(3a) = 2/(3a), so x = (3/2)a hours.

Multiple choice

A leak in the bottom of the container can empty it in 6 hours. A pipe fills in the container at the rate of 4 litres/minute. When the container is full, the inlet in opened but due to the leak, the container is emptied in 8 hours. What is the capacity of the tank?

  1. 8590 litres

  2. 5000 litres

  3. 3750 litres

  4. 2440 litres

  5. 5760 litres
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

It is the correct answer. Solution : Combined 1 hour work of the inlet and leak is 1/8 hour. 1 hour work of inlet = 1/x 1/6 - 1/x = 1/8 x = 24 hour Rate of inlet = 4 litre/minute = 240 litre/hr Capacity of the container = 24*240=5760 litre

Multiple choice

Two pipes A and B can fill a tank in 6 hours. After working at it together for 2 hours, B is closed and A alone fills the remaining part in 8 hours. How many hours will B alone take to fill the tank?

  1. 12

  2. 16

  3. 8

  4. 4 hours

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

Part of tank filled by A and B in 2 hours = 2/6 = 1/3 So in 8 hours, part of the tank filled by A = 1 - 1/3 = 2/3 In 1 hour, part filled by A = 2/(3 * 8) = 1/12 Now, let B take X hours to fill the tank. So, (1/12) + (1/X) = 1/6 X = 12 hours

Multiple choice

A pipe can fill a cistern in 8 hours. Due to a leak at its bottom, it is filled in 9 hours. When the cistern is full, in how much time will it be emptied by the leakage?

  1. 72 hours

  2. 17 hours

  3. 31.5 hours

  4. 64 hours

  5. 36 hours
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Part of the capacity of the cistern emptied by leakage in 1 hour = (1/8 - 1/9) = (9 - 8)/(8 * 9) = 1/72

Therefore, the leakage will take 72 hours to empty the cistern. This is answer correct.

Multiple choice

A reservoir can be filled by 4 pipes in 30, 40, 60 and 120 hours, respectively. The first was opened at 6 am, second was opened at 7 am, third was opened at 8 am and fourth was opened at 9 am. At what time will the reservoir be completely full?

  1. 4 pm

  2. 7 pm

  3. 5 pm

  4. 1:30 pm

  5. 7 am
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let the time taken after 6 am be t hours.
Therefore, (t/30) + ((t - 1)/40) + ((t - 2)/60) + ((t - 3)/120) = 1                  4t + 3(t - 1) + 2(t - 2) + t - 3 = 120                                           t = 13 hours Therefore, the reservoir will be filled at 7 pm.  It is the correct answer.

Multiple choice

A cistern is supported by two pipes. One of them can fill it in 10 minutes whereas the other can empty it in 12 minutes. The cistern is empty & both the pipes are opened at the same time. When will the cistern be full?

  1. 1 hour 10 minutes

  2. 1 hour 12 minutes

  3. 1 hour 8 minutes

  4. 1 hour

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

(Part of the cistern filled in one minute == 1/10 - 1/12 = 6 - 5/60 = 1/60 Therefore, the cistern is full in 60 minutes or in an hour)

Multiple choice

Two pipes A & B can fill a tank in 24 min. & 32 min. respectively . If both the pipe are opened simultaneously, after how much time B should be closed so that the tank is full in 18 min?

  1. 8 minutes

  2. 2 minutes

  3. 9 minutes

  4. 3 minutes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let B be closed after x minutes . Then Part filled by ( A + B ) in x minute + part filled by A in ( 18 - x ) minute = 1 x( 1/24 + 1/32)  + ( 18 - x ) ´ 1/24 = 1 7x/96 + ( 18 - x ) /24 = 1 7x + 4( 18 - x ) = 96 x = 8

Multiple choice

Two pipes A and B can fill a cistern in 16 min and 24 min respectively. Both are opened together at the end of 6 min, A is turned off. in how much time will the cistern be full ?

  1. 22 min

  2. 19 min

  3. 17 min

  4. 15 min

  5. N/A
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Part filled by ( A + B) in 6 min = ( 1/16 + 1/24 ) x 6 = 5/ 48 x 6 =5/8 Remaining part = ( 1 - 5/8 ) = 3/8 1/24 part is filled by B in i min. 3/8 part is filled by B in (24 x 3/8) =9 min Therefore total time taken to fill the cistern = (6 + 9) =15 min