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 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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3 2221
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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4 2205
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 2008
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 1878
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 1544
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 1502
Q:

Two pipes X and Y can fill an empty tank in 16 hours and 20 hours respectively. Pipe Z alone can empty the completely filled tank in 25 hours. Firstly both pipes X and Y are opened and after 6 hours pipe Z is also opened. What will be the total time (in hours) taken to completely fill the tank?

 

A) 80/7 B) 67/7
C) 28/3 D) 304/29
 
Answer & Explanation Answer: D) 304/29

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0 1298
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 1244