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:

Pipes A and B can fill a cistern in 15 hours together. But ifthese pipes operate separately A takes 40 hours less than Bto fill the tank. In how many hours the pipe A will fill thecistern working alone?

A) 60 B) 20
C) 40 D) 15
 
Answer & Explanation Answer: B) 20

Explanation:

Let A takes x hours, then B = (x+40) hours

1/x + 1/x+40 = 1/15

x = 20

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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

Explanation:
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4 2126
Q:

A cistern has one inlet, L and one inlet, M. L takes 5 hours to fill the empty tank, when M is not open and M takes 8 hours to empty the full tank, if the tank is two fifth full, how much time will it take to fill the tank completely when both L and M are opened simultaneously? (in hours)

A) 5 hours B) 3 hours
C) 6 hours D) 8 hours
 
Answer & Explanation Answer: D) 8 hours

Explanation:
If the tank is 2/5th full, then remaining empty tank will be = 1-2/5=3/5th
L and M can fill the empty tank in = (5*8)/(8-5)=40/3 hours

Then 3/5 th tank fill in =40/3 * 3/5= 8 hours

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2 1953
Q:

18 buckets of water fill a tank when the capacity of each bucket is 8 litres. How many buckets will be needed to fill the same tank, if the capacity of the bucket is 12 litres?

A) 12 B) 13.5
C) 24 D) Data insufficient
 
Answer & Explanation Answer: A) 12

Explanation:

Capacity of tank = (8 X 18) = 144 litres

If the capacity of each bucket = 12 litres

Then, Nunber of buckets needed = 144 / 12 = 12 buckets

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3 1774
Q:

An electric pump can fill a tank in 2 hours. Because of a leak in the tank, it was taking 21⁄2 hours to fill the tank. The leak can drain all the water off the tank in how many hours?

A) 9 B) 10
C) 10.5 D) 11.5
 
Answer & Explanation Answer: B) 10

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6 1491
Q:

Two taps P and Q can fill a tank in 24 hours and 18 hours respectively. If the two taps are opened at 11 a.m., then at what time (in p.m.) should the tap P be closed to completely fill the tank at exactly 2 a.m.?

A) 5 B) 2
C) 3 D) 4
 
Answer & Explanation Answer: C) 3

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12 1440
Q:

Three pipe P, Q and R can fill a tank in 12 minutes, 18 minutesand 24 minutes respectively. The pipe R is closed 12 minutesbefore 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
 
Answer & Explanation Answer: B) 8 (4/13) hrs

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3 1194
Q:

A water tank is 2/5 th full. Inlet A can fill the tank in 12 minutes while an outlet pipe B can empty it in 6minutes. If both the pipes are open, how long will it take to empty or fill the tank completely?

A) It fills in 4.8 min B) It empties in 4.8 min
C) It fills in 5.6 min D) It empties in 5.6 min
 
Answer & Explanation Answer: B) It empties in 4.8 min

Explanation:
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