Pipes and Cistern Questions

FACTS  AND  FORMULAE  FOR  PIPES  AND  CISTERN  QUESTIONS

 

 

1. Inlet : A pipe connected with a tank or a cistern or a reservoir, that fills it, is known as an inlet.

 

2. Outlet : A pipe connected with a tank or cistern or reservoir, emptying it, is known as an outlet.

 

(i) If a pipe can fill a tank in x hours, then:

part filled in 1 hour = 1/x

(ii) If a pipe can empty a tank in y hours, then:

part emptied in 1 hour = 1/y

(iii) If a pipe can fill a tank in x hours and another pipe can empty the full tank in y hours (where y > x), then on opening both the pipes, then the net part filled in 1 hour = 1x-1y

(iv) If a pipe can fill a tank in x hours and another pipe can empty the full tank in y hours (where x > y), then on opening both the pipes,  the net part emptied in 1 hour = 1y-1x

Q:

Two filling taps P and Q together can fill a tank with rate of 40 lit/min and 60 lit/min respectively in 8 min. If a waste tap can empty the filled tank in 32 min, then what is the rate of waste tap ?

A) 34 lit/min B) 25 lit/min
C) 22 lit/min D) 18 lit/min
 
Answer & Explanation Answer: B) 25 lit/min

Explanation:

Given that the waste tap can empty the filled tank in 32 min.

Now, the rate at which the waste tap can empty the tank = (40 + 60)8/32 = 100/4 = 25 lit/min.

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Q:

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

A) 85 min B) 92 min
C) 187 min D) 144 min
 
Answer & Explanation Answer: D) 144 min

Explanation:

Let the slower pipe alone fill the tank in x min.

Then, faster pipe will fill it in x/3 min.

1/x + 3/x = 1/36 

4/x = 1/36 => x = 144 min.
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Q:

Pipe A is an inlet pipe that can fill an empty cistern in 69 hours. Pipe B can drain the filled cistern in 46hours. When the cistern was filled the two pipes are opened one at a time for an hour each, starting withPipe B. how long will it take for the cistern to be empty?

A) 11 days 10 hours B) 11 days 7 hours
C) 11 days 12 hours D) 1 days 13 hours
 
Answer & Explanation Answer: B) 11 days 7 hours

Explanation:
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Q:

A water tank has holes. The 1st hole alone empties the tank in 9 min and 2nd hole alone empties the tank in 6 min. If water leaks out at a constant rate, how many min does it take if both the holes together empty the tank?

A) 3 3/5 B) 3/5
C) 3 1/5 D) 3 2/5
 
Answer & Explanation Answer: A) 3 3/5

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Q:

A water tank is filled in 5 hours by three pipes X, Y and Z the pipe Z is thrice as fast as Y and Y is twice as fast as X. How much time will pipe X alone take to fill the water tank?

A) 60 hrs B) 45 hrs
C) 40 hrs D) 35 hrs
 
Answer & Explanation Answer: B) 45 hrs

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Q:

3 pipes when opened for 3 hours can fill 3 buckets. How many buckets can 2 pipes open for 2 hours approximately fill?

A) 2/3 buckets B) 2 buckets
C) 1 bucket D) 4/3 bucket
 
Answer & Explanation Answer: D) 4/3 bucket

Explanation:

2 pipes open for 2 hours will fill = (2/3) x (2/3) x 3 = 4/3 buckets

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9 2024
Q:

Two pipes, when working one at a time, can fill a cistern in 3 hhrs and 4 hrs, resp while a third pipe can drain the cistern empty in 8 hrs. All the three pipes were opened together when the cistern was 1/12 full. How long did it take for the cistern to be completely full?

A) 2 hrs B) 1 hr 45 min
C) 2 hr 10 min D) 2 hr 11 min
 
Answer & Explanation Answer: A) 2 hrs

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Q:

Two taps X and Y can fill a tank in 15 hours and 20 hours respectively. If the two taps are opened at 2 p.m., then at what time (in p.m.) should the tap X be closed to completely fill the tank at exactly 2 a.m.?

A) 8 B) 7
C) 9 D) 10
 
Answer & Explanation Answer: A) 8

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