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

How much time a tank would take to be filled by 3 pipes which diameters are 2 cm, 3 cm and 4 cm running together, when the largest pipe alone takes 58 minutes time to fill the tank. [Note:The amount of water flowing in each pipe is proportional to the square of its diameter.]

  1. 25 minutes.

  2. 30 minutes.

  3. 27 minutes

  4. 32 minutes

  5. 28 minutes
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Flow is proportional to d^2. Flow rates: 4, 9, 16. Largest pipe (16) fills in 58 mins. Tank capacity = 16 * 58 = 928 units. Total flow rate = 4 + 9 + 16 = 29. Time = 928 / 29 = 32 minutes.

Multiple choice

Arlo works with a water supply corporation. Due to a power cut in an area, the corporation has to send a water tank in order to fulfill the residents' water needs. So, Arlo puts five inlet pipes in the tank in order to fill it with water. Out of the five pipes, three have narrow openings and two have wide openings. The rate at which the narrow pipes work is half the rate of the pipes with wide openings. If all the pipes work together, then they will take what fraction of the time taken by the two wide pipes working together to fill the tank?

  1. 4 7

  2. 3 7

  3. 7 4

  4. 7 3

  5. 2 7
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let each wide pipe fill at rate 2r and each narrow pipe at rate r. All five together fill at 3r + 4r = 7r, while the two wide pipes fill at 4r. The ratio of times is (1/7r)/(1/4r) = 4/7. Option A is meant to represent 4/7.

Multiple choice

A constructor builds a water tank with the dimensions 100 m long and 75 m wide. He uses a square pipe with sides 20 cm to fill the water into it. If the water level rises by 1.2 m in 10 hours while filling the tank with the square pipe, then what will be the speed of water?

  1. 21 km per hour

  2. 22.5 km per hour

  3. 23.5 km per hour

  4. 24 km per hour

  5. 26 km per hour
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Volume of water = 100 * 75 * 1.2 = 9,000 m^3. Pipe area = 0.2 * 0.2 = 0.04 m^2. Flow rate = Volume / Time = 9,000 / 10 = 900 m^3/hr. Speed = Flow rate / Area = 900 / 0.04 = 22,500 m/hr = 22.5 km/hr.

Multiple choice

The efficiency of inlet pipe P is 20% more than that of the inlet pipe Q so the pipe P takes 24 minutes less to fill a water tank of capacity 6000 litres. Quantity I : How much time, the pipe P and the pipe Q together will take to fill a water tank of capacity 8800 litres? Quantity II : 99 minutes

  1. Quantity : I > Quantity : II

  2. Quantity : I ≥ Quantity : II

  3. Quantity : I < Quantity : II

  4. Quantity : II ≥ Quantity : I

  5. Quantity I = Quantity II or relation can't be established
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let efficiency of Q be x, P be 1.2x. Time taken by P = 6000/1.2x = 5000/x. Time taken by Q = 6000/x. Difference = 1000/x = 24 mins. x = 1000/24 = 125/3. Time for P and Q together for 8800L = 8800 / (x + 1.2x) = 8800 / 2.2x = 4000 / x = 4000 / (125/3) = 4000 * 3 / 125 = 32 * 3 = 96 minutes. Since 96 < 99, Quantity I < Quantity II.

Multiple choice

A cistern has two inlets A and B which can be filled in 12 minutes and 15 minutes, respectively. An outlet C can empty the full cistern in 10 minutes. If all the three pipes are opened together in the empty cistern, then the time taken to fill the cistern completely is__________.

  1. 20 minutes

  2. 10 minutes

  3. 15 minutes

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

The rates of the inlets A and B are 1/12 and 1/15 of the cistern per minute, respectively, while the outlet C empties at a rate of 1/10 per minute. When all three are opened together, the net rate of filling per minute is 1/12 + 1/15 - 1/10 = 3/60 = 1/20. Therefore, it will take 20 minutes to fill the cistern completely.

Multiple choice

Consider three pipes A, B and C connected to a tank. All three pipes can fill the tank in 6 hours. Pipe C is taken off after working at it for two hours and pipes A and B fill the remaining part of the tank in 7 hours. Determine the time required to fill the tank alone by pipe C.

  1. 6 hours

  2. 9 hours

  3. 14 hours

  4. 21 hours

  5. Cannot be determined
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A+B+C = 1/6. In 2 hours, they fill 2/6 = 1/3. Remaining = 2/3. A+B fill 2/3 in 7 hours, so A+B = (2/3)/7 = 2/21. C = (A+B+C) - (A+B) = 1/6 - 2/21 = 7/42 - 4/42 = 3/42 = 1/14. C takes 14 hours.

Multiple choice

Directions: The question below consists of two statements labelled (I) and (II). You have to decide whether the data provided in the statements is sufficient to answer the question. Two taps P and Q together take 3 min 36 sec to fill a tank. How many minutes does a drain pipe R take to empty the tank when it is full? (I) P and R can fill the tank in 9 min. (II) Q alone takes 9 min to fill the tank. Mark your answer as:

  1. If the question can be solved using only one of the statements

  2. If the question can be solved using either of the statements

  3. If the question can be solved using both the statements but not either alone

  4. If the question cannot be solved using the given statements
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let the tank capacity be 1 unit. P+Q fill at 1/3.6 = 5/18 units/min. Statement (II) says Q fills at 1/9 units/min, so P fills at 5/18 - 2/18 = 3/18 = 1/6 units/min. Statement (I) says P-R fills at 1/9 units/min, so R empties at 1/6 - 1/9 = 1/18 units/min. Both statements are required to find R's rate.

Multiple choice

There are two inlets A and B connected to a tank. A and B can fill the tank in 32 hours and 28 hours, respectively. If both the pipes are opened alternately for 1 hour, starting with A, then in how much time (in hours, to nearest integer) will the tank be filled?

  1. 22

  2. 30

  3. 36

  4. 24
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In 2 hours (one cycle of A then B), the tank fills 1/32 + 1/28 = 15/224 of the tank. After 28 cycles (56 hours), 28 * (15/224) = 15/8 = 1.875, which is impossible as the tank capacity is 1. We calculate the work done cycle by cycle until the tank is full, leading to 30 hours.

Multiple choice

A cylindrical reservoir of diameter 112 meters and height 28 meters is full of water. A cylindrical pipe is connected to the reservoir to empty a tank, which has a diameter of 7 meters and takes 256 minutes to empty the tank. Quantity A: Rate of water flow per minute Quantity B: 9 meters/minute

  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