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

Pipe A can fill a tank in 12 hours and pipe B can empty the tank in 18 hours. Both pipes are opened at 6 AM and after some time, pipe B is closed and tank is full at 8 PM. At what time was the pipe B closed?

  1. 10 AM

  2. 8 AM

  3. 9 AM

  4. 11 AM
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let pipe B be closed after x hours. Pipe A runs for 14 hours (6 AM to 8 PM). Pipe A fills 14/12 of the tank. Pipe B empties x/18 of the tank. Since the tank is full, 14/12 - x/18 = 1. 7/6 - x/18 = 1. x/18 = 1/6. x = 3 hours. 6 AM + 3 hours = 9 AM.

Multiple choice

Rohit purchased a cistern which had a leakage. The cistern can be filled by two inlet pipes, which can individually fill the cistern in 12 min and 15 min, respectively. Despite leakage, the two inlet pipes together can fill the cistern in 20 min. How long will it take to empty the completely full cistern due to leakage?

  1. 10 min.

  2. 12 min.

  3. 15 min.

  4. 16 min.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Inlet 1 rate = 1/12, Inlet 2 rate = 1/15. Combined inlet rate = 1/12 + 1/15 = 5/60 + 4/60 = 9/60 = 3/20. With leakage, rate = 1/20. Leakage rate = Combined inlet rate - Net rate = 3/20 - 1/20 = 2/20 = 1/10. Time to empty = 10 min.

Multiple choice

Two pipes A and B can fill a cistern in 120 minutes and 150 minutes, respectively. There is also an outlet C. If all the three pipes are opened together, the cistern gets filled in 100 minutes. How much time will be taken by C to empty full tank?

  1. 3 h 20 min

  2. 2 h 40 min

  3. 3 h

  4. 3 h 40 min
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A rate = 1/120, B rate = 1/150. Combined A+B = 1/120 + 1/150 = 9/600 = 3/200. With C, A+B-C = 1/100. So 3/200 - C = 2/200. C = 1/200. Time = 200 minutes = 3 hours 20 minutes.

Multiple choice

Water from a tank moves through a pipe to fill a swimming pool. Pipes P and Q can fill a cylindrical tank in 24 min and 32 min, respectively. Both pipes are opened. After what time should pipe Q be closed, so that the tank is full in 18 minutes?

  1. 8 minutes

  2. 9 minutes

  3. 6 minutes

  4. 10 minutes

  5. 11 minutes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let Q be closed after x minutes. Pipe P works for 18 minutes, filling 18/24 = 3/4 of the tank. Pipe Q works for x minutes, filling x/32 of the tank. 3/4 + x/32 = 1 implies x/32 = 1/4, so x = 8.

Multiple choice

Water flows into a tank 180 m × 140 m through a rectangular pipe of 1.2 m × 0.75 m at a rate of 15 km/h. In what time will the water rise by 4 m?

  1. 7 hours 28 minutes

  2. 6 hours 42 minutes

  3. 8 hours 12 minutes

  4. 5 hours 46 minutes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Volume of water needed = 180 * 140 * 4 = 100,800 cubic meters. Flow rate of pipe = 1.2 * 0.75 * 15,000 = 13,500 cubic meters per hour. Time = 100,800 / 13,500 = 7.4666 hours, which is 7 hours and 28 minutes.

Multiple choice

Pipe A, B and C fill a tank alone in 10,15 and 20 min respectively. All the pipe open for 3 min than pipe C is closed than find in how many min pipe A and B can fill the rest of the part?

  1. 12.3

  2. 22.5

  3. 2.1

  4. 3.3

  5. 3.36
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Rates: A=1/10, B=1/15, C=1/20. Combined rate = 6/60 + 4/60 + 3/60 = 13/60. In 3 mins, they fill 3 * 13/60 = 39/60 = 13/20. Remaining part = 7/20. Rate of A+B = 1/10 + 1/15 = 3/30 + 2/30 = 5/30 = 1/6. Time = (7/20) / (1/6) = 42/20 = 2.1 minutes.

Multiple choice

Pipe A can fill the tank in 4 hours, while pipe B can fill it in 6 hours working separately. Pipe C can empty whole the tank in 4 hours. He opened the pipe A and B simultaneously to fill the empty tank. He wanted to adjust his alarm so that he could open the pipe C when it was half-filled, but he mistakenly adjusted his alarm at a time when his tank would be 3/4th filled. What is the time difference between both the cases, to fill the tank fully:

  1. 48 min.

  2. 54 min.

  3. 30 min.

  4. None of these

  5. Can't be determined
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice

A tank is fitted with 2 inlet pipes A and B. Both pipes are kept open for 15 minutes to fill 3/5 of the tank and pipe A is closed. If pipe A is thrice as fast as pipe B. How much time will be taken by B alone to complete the remaining work?

  1. 45min

  2. 50 min

  3. 40 min

  4. 30 min

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

A is 3 times as fast as B. In 15 mins, they fill 3/5. Rate(A+B) = (3/5) / 15 = 1/25 tank/min. Since A=3B, 4B = 1/25, so B = 1/100 tank/min. Remaining 2/5 tank takes (2/5) / (1/100) = 40 minutes.

Multiple choice

Three pipes P1, P2 and P3 can fill a glass tub from empty to full in 30 minutes, 20 minutes, and 10 minutes respectively. When the glass tub is empty, all the three pipes are opened. P1,P2 and P3 discharge chemical solutions C, H and T respectively. What is the proportion of the solution T in the liquid in the pot after 3 minutes?

  1. 11/6

  2. 5/11

  3. 6/11

  4. 1/11

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

In 3 minutes, P1 fills 3/30 = 1/10 of the tub, P2 fills 3/20, and P3 fills 3/10. Total volume = 1/10 + 3/20 + 3/10 = (2+3+6)/20 = 11/20. The proportion of T is (3/10) / (11/20) = (3/10) * (20/11) = 6/11.