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# Two pipes can fill a cistern in 30 and 15 hours respectively

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Joined: 18 Dec 2017
Posts: 819
Location: United States (KS)
Two pipes can fill a cistern in 30 and 15 hours respectively  [#permalink]

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30 Nov 2019, 09:35
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Difficulty:

35% (medium)

Question Stats:

71% (02:05) correct 29% (03:35) wrong based on 7 sessions

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Two pipes can fill a cistern in 30 and 15 hours respectively. The pipes are opened simultaneously and it is found that due to leakage in the bottom, 5 hrs extra are taken for the cistern to be filled up. If the cistern is full, in what time would the leak alone empty it ?

A. 60 hrs
B. 45 hrs
C. 35 hrs
D. 30 hrs
E. None of these

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Re: Two pipes can fill a cistern in 30 and 15 hours respectively  [#permalink]

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30 Nov 2019, 10:48
TheNightKing wrote:
Two pipes can fill a cistern in 30 and 15 hours respectively. The pipes are opened simultaneously and it is found that due to leakage in the bottom, 5 hrs extra are taken for the cistern to be filled up. If the cistern is full, in what time would the leak alone empty it ?

A. 60 hrs
B. 45 hrs
C. 35 hrs
D. 30 hrs
E. None of these

Let the capacity of the tank be 30

So, Efficiency of the pipes are 2 and 1 = 3 units/hr

Hence , Total time required by the 2 pipes to fill the tank is 30/3 = 10

But, due to leakage time taken is 15 hours, so the combined efficiency becomes 30/15 = 2 units/hr

The reduction in effciciency ( 3 - 2 = 1 unit/hr) is due to the leakage in the bottom, so the time taken by the outlet/leakage pipe to empty the cistern is 30/1 = 30 Hours , Answer must be (D)
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Re: Two pipes can fill a cistern in 30 and 15 hours respectively   [#permalink] 30 Nov 2019, 10:48
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