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 Pipes and Cistern Questions

Popular Latest Rated Important Formulae

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:

One fill pipe A is 3 times faster than second fill pipe B and takes 32 minutes less than the fill pipe B. When will the cistern be full if both pipes are opened together?

A) 6 min B) 8 min
C) 12 min D) 10 min
 
Answer & Explanation Answer: C) 12 min

Explanation:

Let pipe A takes p min to fill

Then,

pipe B takes 3p min to fill

=> 3p - p = 32

=> p = 16 min => 3p = 48 min

 

Required, both pipes to fill = (48 x 16)/(48 + 16) min = 12 min.

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18 10891
Q:

Water flows into a tank which is 200 m long and 150 m wide, through a pipe of cross-section (0.3m x 0.2m) at 20 km/h. In what time will the water level be 12m  ?

A) 200 hrs B) 240 hrs
C) 300 hrs D) 270 hrs
 
Answer & Explanation Answer: C) 300 hrs

Explanation:

Volume of water collected in the tank in 1 hour

⇒ (0.3 × 0.2 × 20km × 1000mts) = 1200 m cubic

If after t hours, the water is at height of 12m,

1200t=200×150×12 

⇒ t = 300 Hours.

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25 10135
Q:

A and B can fill the tank in 60 min and 90 min. There is a leak at 3/4th of the height. If leak is opened alone, it takes 36 min to empty till 3/4th the height. Find the time taken to fill the tank if all of the taps and the leak are opened simultaneously.

A) 39 B) 27
C) 37 D) 33
 
Answer & Explanation Answer: A) 39

Explanation:
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50 9191
Q:

In what time would a cistern be filled by three pipes which diameters are 2 cm, 3 cm and 4 cm running together, when the largest alone can fill it is 58 minutes? The amount of water flowing in each pipe is proportional to the square of its diameter.

A) 26 min B) 32 min
C) 36 min D) 42 min
 
Answer & Explanation Answer: B) 32 min

Explanation:

Given that the diameters of the three pipes are 2 cm, 3 cm and 4 cm

From the given data,

Amount of water from three pipes is 4 units, 9 units and 16 units.

Let the capacity of cistern be 'p' units.

∴ p/58 = 16

⇒ p = 928 units.

 

In 1 minute, quantity to be filled by 3 pipes = 29 units

∴ Total time required = 928/29 = 32 minutes.

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10 9166
Q:

Two pipes A and B can fill a tank in 15 min and 20 min respectively. Both the pipes are opened together but after 4 min, pipe A is turned off. What is the total time required to fill the tank ?

A) 15 min 20 sec. B) 16 min 40 sec.
C) 13 min 10 sec. D) 14 min 40 sec.
 
Answer & Explanation Answer: D) 14 min 40 sec.

Explanation:

Part filled in 4 minutes = 4(1/15 + 1/20) = 7/15

 

Remaining part = 1 - 7/15 = 8/15

 

Part filled by B in 1 minute = 1/20

 

1/20 : 8/15 :: 1 : k

 

k = (8/15 )x 1 x 20 = 10( 2/3) min = 10 min 40 sec.

 

The tank will be full in (4 min. + 10 min. 40 sec) = 14 min 40 sec.

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7 8160
Q:

Three taps I, J and K can fill a tank in 20,30and 40 minutes respectively. All the taps are opened simultaneously and after 5 minutes tap A was closed and then after 6 minutes tab B was closed .At the moment a leak developed which can empty the full tank in 70 minutes. What is the total time taken for the completely full ?

A) 24.315 minutes B) 26.166 minutes
C) 22.154 minutes D) 24 minutes
 
Answer & Explanation Answer: B) 26.166 minutes

Explanation:

Upto first 5 minutes I, J and K will fill => 5[(1/20)+(1/30)+(1/40)] = 65/120


For next 6 minutes, J and K will fill => 6[(1/30)+(1/40)] = 42/120


So tank filled upto first 11 minutes = (65/120) + (42/120) = 107/120
So remaining tank = 13/120


Now at the moment filling with C and leakage @ 1/60 per minute= (1/40) - (1/70) = 3/280.
So time taken to fill remaining 13/120 tank =(13/120) /(3/280) = 91/6 minutes

 

Hence total time taken to completely fill the tank = 5 + 6 + 91/6 = 26.16 minutes.

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13 7550
Q:

Two pipes A and B can separately fill a cistern in 60 min and 75 min respectively. There is a third pipe in the bottom of the cistern to empty it. If all the three pipes are simultaneously opened, then the cistern is full in 50 min. In how much time, the third pipe alone can empty the cistern ?

A) 85 min B) 95 min
C) 105 min D) 100 min
 
Answer & Explanation Answer: D) 100 min

Explanation:

Work done by the third pipe in 1 min = 1/50 - (1/60 + 1/75) = - 1/100.
[-ve sign means emptying]

The third pipe alone can empty the cistern in 100 min.

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7 7507
Q:

There is an empty reservoir whose capacity is 30 litres. There is an inlet pipe which fills at 5 L/min and there is an outlet pipe which empties at 4 L/min. Both the pipes function alternately for 1 minute. Assuming that the inlet pipe is the first one to function, how much time will it take for the reservoir to be filled up to its capacity?

A) 49.5 min B) 50 min
C) 51 min D) 52 min
 
Answer & Explanation Answer: C) 51 min

Explanation:

The work to be done = Capacity of reservoir  = 30 litres.

 1st Minute ---> inlet pipe opened ---> 5 lit filled

 2nd minute ---> inlet pipe closed; outlet pipe opened ---> 4 lit emptied

 

In 2 minutes (5 litres - 4 litres = 1lit) is filled into the reservoir.

It takes 2 minutes to fill 1lit ---> it takes 50 minutes to fill 25 litres into the reservoir.  

 

In the 51st minute inlet pipe is opened and the reservoir is filled.

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24 7269