Hello Aspirants. Welcome to Online Quantitative Aptitude Section with explanation in AffairsCloud.com. Here we are creating question sample in **Pipes & CisternÂ **which is common for all competitive exams. We have included Some questions that are repeatedly asked in bank exams !!!

Questions Penned by Yogit

**Two pipes A and B can fill a tank in 10 hours and 15 hours respectively while a third pipe C can empty the full tank in 20 hours. All the pipes are opened for 5 hours and then C is closed. Find the time in which the tank is full?**

a) 5.5 hrs

b) 6.5 hrs

c) 7.5 hrs

d) 8.5 hrs

e) None of theseAnswer –**c) 7.5 hrs**

**Explanation :**

(1/10 + 1/15 â€“ 1/20)*5 + (1/10 + 1/15)*T = 1. We will get T = 2.5 hrs

so total time = 5 + 2.5 = 7.5 hrs**Three pipe P, Q and R can fill a tank in 12 minutes, 18 minutes and 24 minutes respectively. The pipe R is closed 12 minutes before the tank is filled. In what time the tank is full?**

a) 8.(5/13) hrs

b) 8.(4/13) hrs

c) 7.(4/13) hrs

d) 8.(6/13) hrs

e) None of theseAnswer –**b) 8.(4/13) hrs**

**Explanation :**

Let T is the time taken by the pipes to fill the tank

(1/12 + 1/18 + 1/24)*(T – 12) + (1/12 + 1/18)*12 = 1

We will get T = 108/13 = 8.(4/13) hrs**On pipe P is 4 times faster than pipe Q and takes 45 minutes less than pipe Q. In what time the cistern is full if both the pipes are opened together?**

a) 8 minutes

b) 10 minutes

c) 12 minutes

d) 14 minutes

e) None of theseAnswer –**c) 12 minutes**

**Explanation :**

Let P takes x minutes to fill the tank alone, then Q will take 4x minutes to fill the tank

4x â€“ x = 45, x = 15

So P will take 15 minutes and Q will take 60 minutes to fill the tank. Both will fill the tank in

(60*15)/(75) = 12 minutes**Two pipes can fill a tank in 15 and 20 hours respectively. The pipes are opened simultaneously and it is found that due to the leakage in the bottom, 17/7 hours extra are taken extra to fill the tank. If the tank is full, in what approximate time would the leak empty it?**

a) 27 hrs

b) 32 hrs

c) 36 hrs

d) 39 hrs

e) None of theseAnswer –**d) 39 hrs**

**Explanation :**

Total time taken by both pipes before the leak was developed = 60/7 hours

now, leaks is developed which will take T time to empty the tank so, (1/15 +1/20 â€“ 1/T) = 1/11

solve for T, we will get 660/17 hours = 39 hours (approx.)**Two pipes A and B can fill a tank in 8 minutes and 12 minutes respectively. If both the pipes are openedsimultaneously, after what time should B be closed so that the tank is full in 6 minutes?**

a) 1 min

b) 2 min

c) 3 min

d) 4 min

e) None of theseAnswer –**c) 3 min**

**Explanation :**

Let after x minutes pipe B is closed

(1/8 + 1/12)*x + (1/8)*(6 -x) = 1

X= 3 minutes**In what time would a cistern be filled by three pipes whose diameters are 1cm, 2 cm and 3 cm running together, when the largest pipe alone can fill the tank in 21 minutes? The amount of water flowing through the pipe is directly proportional to the square of its diameter.**

a)10.5 minutes

b) 11.5 minutes

c) 12.5 minutes

d) 13.5 minutes

e) None of theseAnswer –**d) 13.5 minutes**

**Explanation :**

More the diameter more will be the water flowing through it and less will be the time taken.

Means bigger pipe will take less time to fill the tank

So, for 1 cm time, (1^2)/(3^2) = 21/t, we get t = 189

For 2 cm time, (2^2)/(3^2) = 21/t. We get t = 189/4

So total time = 1/21 + 1/189 + 4/189 = 2/27

So total time = 13.5 minutes**Two pipes P and Q can fill a tank in 10 min and 12 min respectively and a waste pipe can carry off 12 litres of water per minute. If all the pipes are opened when the tank is full and it takes one hour to empty the tank. Find the capacity of the tank.**

a) 30

b) 45

c) 60

d) 75

e) None of theseAnswer –**c) 60**

**Explanation :**

Let the waste pipe take â€˜Tâ€™ time to empty the tank.

(1/10 + 1/12 â€“ 1/T)*60 = -1

We will get T = 5 min

So capacity = 5*12 = 60ltr**One pipe fill 1/4 of the tank in 4 minutes and another pipe fills 1/5 of the tank in 4 minutes. Find the time taken by both pipe together to fill half the tank?**

a) 40/9 minutes

b) 50/9 minutes

c) 44/9 minutes

d) 53/9 minutes

e) None of theseAnswer –**a) 40/9 minutes**

**Explanation :**

First pipe will take 16 minutes to fill the tank alone. Similarly second pipe will take 20 minutes to fill the tank alone. Let T is the time in which both the pipes will fill half the tank

(1/16 + 1/20)*T = 1/2, we get T = 40/9 minutes**Two pipes can separately fill the tank in 15hrs and 30hrs respectively. Both the pipe are opened and when the tank is 1/3 full a leak is developed due to****which 1/3 water supplied by the pipe leaks out. What is the total time to fill the tank?**

a) 20/3 hr

b) 35/3 hr

c) 40/3 hr

d) 50/3 hr

e) None of theseAnswer –**c) 40/3 hr**

**Explanation :**

(1/15 + 1/30)*T1 = 1/3, T1 = 10/3 hr

Now after leak is developed, [(1/15 + 1/30) â€“ (1/3)*(1/15 + 1/30)]*T2 = 2/3

T2 = 10 hr. So total time = 10 + 10/3 = 40/3 hr**Three pipes A, B and C is attached to a cistern. A can fill it in 20 minutes and B can fill it in 30 minutes. C is a waste pipe.Â After opening both the pipes A and B, Riya leaves the cistern to fill and returns when the cistern is supposed to be filled. But she found that waste pipe C had been left open, she closes it and now the cistern takes 5 minutes more to fill. In how much time the pipe C can empty the full cistern?**

a) 26.8 minutes

b) 25.8 minutes

c) 27.8 minutes

d) 28.8 minutes

e) None of theseAnswer –**d) 28.8 minutes**

**Explanation :**

The tank supposed to be filled in (30*20)/50 = 12 minutes

so, (1/20 + 1/30)*12 â€“ 12/C + (1/20 + 1/30)*5 = 1 (A and B work for 12 minutes and also C work for 12 minutes and then A and B takes 5 more minutes to fill the tank)

solve for C, we will get C = 144/5 = 28.8

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