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Pipes and Cistern ( 16 to 20 ):

# APTITUDE QUESTIONS (PIPES AND CISTERN):

16. Bucket A has thrice capacity as bucket B. it takes 60 turns for bucket A to fill the empty drum. How many turns will it take for both the buckets A and B, having each turn together to fill the empty drum?

A) 50

B) 40

C) 45

D) 90

E) None of these

View Answer

Answer: option (C)

Explanation:

Let capacity of A be x litres. Then, capacity of B = x/3 litres

Capacity of the drum = 60x litres

Required number of turns = ( 60x / x+(x/3)) = (60x * 3/4x) = 45

17. Two pipes P and Q can fill a tank in 12 minutes and 15 minutes respectively. How much more time will it take to fill the tank by tap Q if both the taps are opened simultaneously and the tap P is closed after 3 minutes?

A) 9 min 15 sec

B) 9 min 45 sec

C) 8 min 5 sec

D) 8 min 15 sec

E) None of these

View Answer

Answer: option (D)

Explanation:

Part filled in 3 min = 3((1/12)+(1/15)) = ( 3 * (9/60)) = 9/20

Remaining part = (1- (9/20)) = 11/20

Part filled by Q in 1 min = 1/15

1/15 : 11/20 : : 1 : x or x = ((11/20)*1*15) = 8(1/4) min = 8 min 15 sec

∴Remaining part is filled by Q in 8 min 15 sec

18. Two pipes X and Y can fill a tank in 15 hours and 20 hours respectively while a third pipe Z can empty the full tank in 25 hours. All the three pipes were opened in the starting. After 10 hours, Z is closed. In how much time, will the tank be full?

A) 12 hrs

B) 13 hrs

C) 16 hrs

D) 18 hrs

E) None of these

View Answer

Answer: option (A)

Explanation:

Part filled in 10 hours = 10((1/15)+(1/20)-(1/25)) = 23/30

Remaining part = (1- (23/30)) =7/30

(X + Y)’s 1 hours work = (1/15)+(1/20)) = 7/60

7/60 : 7/30 : : 1 : x or x = ((7/30)*1*(60/7)) = 2 hours

therefore the tank will be full in (10 + 2) hrs = 12 hours

19. A large tanker can be filled by two pipes X and Y in 60 minutes and 40 minutes respectively. How many minutes will it take to fill the tanker from empty state if Y is used for half the time and X and Y fill it together for the other half?

A) 25 min

B) 20 min

C) 27 min

D) 30 min

E) None of these

View Answer

Answer: option (D)

Explanation:

Part filled by (X + Y) in 1 minute = ((1/60)+(1/40)) = 1/24

Suppose the tank is filled in x minutes

Then, x/2((1/24)+(1/40)) = 1 <=> x/2 * 1/15 = 1 <=> x = 30 min

20. Two pipes X and Y can fill a cistern in 12 minutes and 15 minutes respectively while a third pipe Z can empty the full tank in 6 minutes. X and Y are kept open for 5 minutes in the beginning and then Z is also opened. In what time is the cistern emptied?

A) 30 min

B) 33 min

C) 37 min

D) 45 min

E) None of these

View Answer

Answer: option (D)

Explanation:

Part filled in 5 min. = 5((1/12)+1/15)) = (5*(9/60)) = 3/4

Part emptied in 1min when all the pipes are opened = 1/6 – ((1/12)+(1/15)) = ((1/6)-3/20)) = 1/60

Now, 1/60 part is emptied in 1 min

∴ 3/4 part will be emptied in ((60*(3/4)) = 45 min.