100+ Pipes and Cisterns Aptitude Questions and Answers Pdf - 1

Question: 1

A tap can completely fill a water tank in 8 hours. The water tank has a hole in it through which the water leaks out. The leakage will cause the full water tank to get empty in 12 hours. How much time will it take for the tap to fill the tank completely with the hole?

(A) 8 hours

(B) 16 hours

(C) 18 hours

(D) 24 hours

Ans: D

Net part filled in 1 hour = $$({1} / {8} – {1} / {12})$$ = $${1} / {24}$$

∴ The tank will be filled in 24 houirs.

Question: 2

Two pipes A and B can fill a tank in 20 and 30 hours respectively. Both the pipes are opened to fill the tank but when the tank is one third full, a leak develops in the tank through which one third water supplied by both the pipes goes out. The total time taken to fill the tank is

(A) 12 hours

(B) 16 hours

(C) 18 hours

(D) 20 hours

Ans: B

Part filled by (A + B) in 1 hour = $$({1} / {20} + {1} / {30})$$ = $${1} / {12}$$.

So, A and B together can fill the tank in 12 hrs.

$${1} / {3}$$ part is filled by (A + B) in $$({1} / {3} × 12)$$ = 4 hrs.

Since the leak empties one third water, so time taken to fill the tank = Time taken by (A + B) to fill the whole tank + Time taken by (A + B) to fill one – third tank = (12 + 4) hrs = 16 hrs.

Question: 3

An outlet pipe can empty a cistern in 3 hours. In what time will the empty $${2} / {3}$$ part of the cistern?

(A) 2 hours

(B) 3 hours

(C) 4 hours

(D) 5 hours

Ans: B

The outlet pipe empties the one complete cistern in 3 hours.

∴ Time taken to empty $${2} / {3}$$

Part of the cistern = $${2} / {3} × 3$$ = 2 hours.

Question: 4

A cistern can be filled by a tap in 4 hours while it can be emptied by another tap in 9 hours. If both the taps are opened simultaneously, then after how much time will the cistern get filled?

(A) 5 hrs

(B) 6.5 hrs

(C) 7.2 hrs

(D) 9.1 hrs

Ans: C

Net part filled in 1 hour = $$({1} / {4} – {1} / {9})$$ = $$({5} / {36})$$

∴ The cistern will be filled in $${36} / {5}$$ hrs i.e., 72 hrs.

Question: 5

12 buckets of water fill a tank when the capacity of each tank is 13.5 litres. How many buckets will be needed to fill the same tank, if the capacity of each bucket is 9 litres?

(A) 10

(B) 14

(C) 18

(D) 22

Ans: C

Capacity of the tank = (12 × 13.5) litres = 162 litres.

Capacity of each bucket = 9 litres.

Number of buckets needed = $$({162} / {9})$$ = 18.

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