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Pipes and Cistern ( 6 to 10 ):

# APTITUDE QUESTIONS (PIPES AND CISTERN):

6. Pipes X and Y can fill a tank in 5 and 6 hours respectively. Pipe Z can empty it in 12 hours. If all three pipes are opened together then the tank will be filled in how much time?

A) 1(13/17) hours

B) 2(8/11) hours

C) 3(9/17) hours

D) 4(1/2) hours

E) None of these

View Answer

Answer: option (C)

Explanation:

Net part filled in 1 hour = ((1/5)+(1/6)-(1/12)) = 17/60

∴ the tank will be full in 60/17 hrs i.e. 3(9/17) hours

7. Three pipes X, Y and Z can fill a tank from empty to full in 30 minutes, 20 minutes and 10 minutes respectively. When the tank is empty, all the three pipes are opened. X, Y and Z discharge the chemical solutions A, B and C respectively. What is the proportion of solution C in the liquid in the tank after 3 minutes?

A) 5/11

B) 6/11

C) 7/11

D) 8/11

E) None of these

View Answer

Answer: option (B)

Explanation:

Part filled by (X + Y + Z) in 33 minutes = 3(1/30)+(1/20)+(1/10)) = (3*(11/60)) = 11/20

Part filled by Z in 3 minutes = 3/10

∴ ratio = (3/10 * 20/11) = 6/11

8. There are two pipes X and Y which can separately fill a cistern in 60 minutes and 75 minutes respectively and there is a third pipe in the bottom of the cistern to empty it. So, if all the three pipes are simultaneously opened, then the cistern is full in 50 minutes. Then, in how much time the third pipe alone can empty the cistern?

A) 80 min

B) 100 min

C) 90 min

D) 120 min

E) None of these

View Answer

Answer: option (B)

Explanation:

Work done by the third pipe in 1 min = 1/50 – (1/60 + 1/75 ) = ( 1/50 – 3/100) = -1/100

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

9. A pump can fill a tank with water in 2 hours. Because of a leak, it took 2(1/3) hours to fill the tank. The leak can drain all the water of the tank is:

A) 4(1/3) hours

B) 7 hrs

C) 8 hrs

D) 14 hrs

E) None of these

View Answer

Answer: option (D)

Explanation:

Leak in 1 hour = ( 1/2 – 3/7 ) = 1/14

∴ leak will empty the tank in 14 hrs.

10. Two taps X and Y can fill a tank in 5 hours and 20 hours respectively. If both the taps are open due to a leakage, then it took 30 minutes more to fill the tank. How long will it take for the leakage alone to empty the tank if the tank is full?

A) 4(1/2) hours

B) 9 hrs

C) 18 hrs

D) 36 hrs

E) None of these

View Answer

Answer: option (D)

Explanation:

Part filled by (X + Y) in 1 hour = ((1/5)+(1/20)) = 1/4

So, X and Y together can fill the tank in 4 hours.

So, the leak in 1 hour = ((1/4)-(2/9)) = 1/36

Then, leak will empty the tank in 36 hours.