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

**Three pipes A, B, and C can fill the tank in 10 hours, 20 hours and 40 hours respectively. In the beginning all of them are opened simultaneously. After 2 hours, tap C is closed and A and B are kept running. After the 4th hour, tap B is also closed. The remaining work is done by tap A alone. What is the percentage of the work done by tap A alone?**

A. 30 %

B. 35 %

C. 45 %

D. 50 %

E. None of the AboveAnswer –**B. 35 %**

**Explanation :**

Pipe A’s work in % = 100/10 = 10%

Pipe B’s work in % = 100/20 = 5%

Pipe C’s work in % = 100/40 = 2.5%

All of them are opened for 2 hours + after 2 hours, tap C is closed + After the 4th hour, tap B is also closed = 100

=> (10+5+2.5)*2 + (10+5)*2 + X = 100

=> 35 + 30 + work by tap A alone = 100

=> work by tap A alone = 100-65 = 35%**A pipe can fill a tank in 12 minutes and another pipe can fill it in 15 minutes, but a third pipe can empty it in 6 minutes. The first two pipes are kept open for 5 min in the beginning and then third pipe is also opened. Time taken to empty the water tank is?**

A. 30 mins

B. 25 mins

C. 45 mins

D. 50 mins

E. None of the AboveAnswer –**C. 45 mins**

**Explanation :**

x/6 – (x+5)/12 – (x+5)/15 = 0

x = 45 mins**Two pipes A and B can fill a tank in 12 hours and 18 hours respectively. The pipes are opened simultaneously and it is found that due to leakage in the bottom of the tank it took 48 minutes excess time to fill the cistern. When the cistern is full, in what time will the leak empty it?**

A. 72 hours

B. 62 hours

C. 64 hours

D. 84 hours

E. None of the AboveAnswer –**A. 72 hours**

**Explanation :**

Work done by the two pipes in 1 hour = (1/12)+(1/18) = (15/108).

Time taken by these pipes to fill the tank = (108/15)hrs = 7 hours 12 min.

Due to leakage, time taken = 7 hours 12 min + 48 min = 8 hours

Work done by two pipes and leak in 1 hour = 1/8.

Work done by the leak in 1 hour =(15/108)-(1/8)=(1/72).

Leak will empty the full cistern in 72 hours.**A tank is normally filled in 6 hours but takes two hours longer to fill because of a leak in the bottom of the tank. If the tank is full the leak will empty it in how many hours?**

A. 16 hours

B. 18 hours

C. 17 hours

D. 24 hours

E. None of the AboveAnswer –**D. 24 hours**

**Explanation :**

Work done by leak in 1 hr=(1/6-1/8)=1/24

Leak will empty the tank in 24 hours**Twelve pipes are connected to a Cistern. Some of them are inlet pipes and the others are outlet pipes. Each of the inlet pipes can fill the tank in 8 hours and each of the outlet pipes can empty the cistern completely in 6 hours. If all the pipes are kept open, the empty tank gets filled in 24 hours. How many inlet pipes are there?**

A. 6

B. 8

C. 7

D. 4

E. None of the AboveAnswer –**C. 7**

**Explanation :**

(x/8)-[(12-x)/6] = 1/24

x = 7**A dam has four inlets – A, B, C and D. The dam can be filled in 12 minutes through the first three inlets and it can be filled in 15 minutes through the second, the third and fourth inlet also it can be filled through the first and the fourth inlet in 20 minutes. How much time required to fill up the dam by all the four inlets?**

A. 10 mins

B. 15 mins

C. 20 mins

D. 25 mins

E. None of the AboveAnswer –**A. 10 mins**

**Explanation :**

(1/A + 1/B + 1/C) = 1/12 …(i)

(1/B + 1/C + 1/D) = 1/15 …(ii)

(1/A + 1/D) = 1/20 …(iii)

From eqn (i) and (ii)

(1/A – 1/D) = 1/60…(iv)

From eqn (iii) and (iv)

A=30 D=60.

Let the time taken to full the tank = T

T(1/A + 1/B +1/C +1/D)= 1

T(1/30 + 1/15) = 1

T = 10 mins**Three pipes P, Q and R connected to a Cistern. The first pipe (i.e) P can fill 1/2 part of the tank in one hour, second pipe, Q can fill 1/3 part of the cistern in one hour. R is connected to empty the cistern. After opening all the three pipes 7/12 part of the cistern. Then how much time required to empty the cistern completely?**

A. 2 hours

B. 3 hours

C. 4 hours

D. 5 hours

E. None of the AboveAnswer –**C. 4 hours**

**Explanation :**

In 1 hour, P can fill = 1/2 Part

Time taken to fill the Cistern by Pipe P = 2 hours

In 1 hour, Q can fill = 1/3 Part

Time taken to fill the Cistern by Pipe P = 3 hours

[1/2 + 1/3 – 1/R] = 7/12

1/R = 1/4

Time required to empty the Cistern = 4 hours**A Cistern can be filled by an inlet pipe at the rate of 4 litres per minute. A leak in the bottom of a cistern can empty the full tank in 8 hours. When the cistern is full, the inlet is opened and due to the leak, the cistern is empty in 40 hours. How many litres does the cistern hold?**

A. 4000 litre

B. 2400 litre

C. 1920 litre

D. 2020 litre

E. None of the AboveAnswer –**B. 2400 litre**

**Explanation :**

Part emptied by the leak in 1 hour = 1/8

part filled by (leak & inlet open) in 1 hour = 1/40

Part filled by the inlet pipe in 1 hour = 1/8 – 1/40 = 1/10

Inlet pipe fills the tank in = 10 hours

Inlet pipe fills water at the rate of 4 litres a minute.

Capacity of Cistern = 10 * 60 * 4 = 2400 litre**In a tank there is a pipe which can be used for filling the tank as well as for emptying it. The capacity of the tank is 1200 m³. The emptying of the tank is 10 m³ per minute higher than its filling capacity and the pump needs 6 minutes lesser to empty the tank than it needs to fill it. What is the filling capacity of the pipe?**

A. 20 m³ / min.

B. 40 m³ / min.

C. 50 m³ / min.

D. 60 m³ / min.

E. None of the AboveAnswer –**B. 40 m³ / min.**

**Explanation :**

1200/x – 1200/(x+10) = 6

200/x – 200/(x+10) = 6

x2 + 10x – 2000 = 0

x = 40**Two pipes P and Q can fill a cistern in 12 hours and 4 hours respectively. If they are opened on alternate hours and if pipe A is opened first, in how many hours will the tank be full?**

A. 4 hours

B. 5 hours

C. 2 hours

D. 6 hours

E. None of the AboveAnswer –**D. 6 hours**

**Explanation :**

Pipe P can fill = 1/12

Pipe Q can fill = 1/4

For every two hour, 1/12 + 1/4 = 1/3 Part filled

Total = 6 hours

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