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Pipe A and B running together can fill a cistern in 6 minutes. If Pipe [#permalink]
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Updated on: 12 Mar 2016, 08:35
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Pipe A and B running together can fill a cistern in 6 minutes. If Pipe B takes 5 more minutes than Pipe A to fill the cistern, then time in which A and B can fill the cistern separately will be respectively? A. 15 minutes, 20 Minutes. B. 15 minutes, 10 Minutes. C. 12 minutes, 7 minutes. D. 25 minutes, 20 minutes. E. 10 minutes, 15 minutes.
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Originally posted by Why2settleForLess on 12 Mar 2016, 08:15.
Last edited by Bunuel on 12 Mar 2016, 08:35, edited 1 time in total.
Renamed the topic and edited the question.



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Pipe A and B running together can fill a cistern in 6 minutes. If Pipe [#permalink]
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12 Mar 2016, 08:44
Why2settleForLess wrote: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe B takes 5 more minutes than Pipe A to fill the cistern, then time in which A and B can fill the cistern separately will be respectively?
A. 15 minutes, 20 Minutes. B. 15 minutes, 10 Minutes. C. 12 minutes, 7 minutes. D. 25 minutes, 20 minutes. E. 10 minutes, 15 minutes. Let A and B be the times taken by pipes A and B respectively to fill the cistern on their own > B=A+5 Thus, based on the information provided, Cistern filled in 1 minute by A alone + Cistern filled in 1 minute by B alone = Cistern filled in 1 minute \(\frac{1}{A} + \frac{1}{B} = \frac{1}{6}\) \(\frac{1}{A} + \frac{1}{A+5} = \frac{1}{6}\) \(A^27A30=0\) >\(A=10\) minutes and \(B=A+5=10+5=15\) minutes. E is thus the correct answer. FYI, options, B,C and D are automatically out as these options go against the given information of B=A+5, leaving options A and E in the mix. Hope this helps.



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Re: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe [#permalink]
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12 Mar 2016, 08:54
Why2settleForLess wrote: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe B takes 5 more minutes than Pipe A to fill the cistern, then time in which A and B can fill the cistern separately will be respectively?
A. 15 minutes, 20 Minutes. B. 15 minutes, 10 Minutes. C. 12 minutes, 7 minutes. D. 25 minutes, 20 minutes. E. 10 minutes, 15 minutes. Hi, A short and sweet method is being provided by the choices avail..
Its clearly given that B takes 5 more min than A.. so the answer should be x, x+5.. B, C and D can be ELIMINATED as it gives A 5 more minutes..
choices LEFT A. 15 and 20 E. 10 and 15.
If A is the faster and we have B too working at the same speed as A, time taken will be 15/2= 7.5 minutes, which is more than 6 minutes.. so In no way the answer can be 6 as combined effort eliminate A E is the answer
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Re: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe [#permalink]
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12 Mar 2016, 14:13
my gosh, I got into all sorts of equations here.. It sure took more than 3 mins,



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Re: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe [#permalink]
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13 Mar 2016, 07:08
Why2settleForLess wrote: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe B takes 5 more minutes than Pipe A to fill the cistern, then time in which A and B can fill the cistern separately will be respectively?
A. 15 minutes, 20 Minutes. B. 15 minutes, 10 Minutes. C. 12 minutes, 7 minutes. D. 25 minutes, 20 minutes. E. 10 minutes, 15 minutes. Supposing pipe A takes 'x' minutes and pipe 'B' takes y minutes, then A and B together will take x*y/(x+y) minutes. By supposition, x*y = 6(x+y) Plugging in values, we get option E (Note option B is wrong because the values are given in the revers order)



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Re: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe [#permalink]
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13 Mar 2016, 07:10
Mathivanan Palraj wrote: Why2settleForLess wrote: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe B takes 5 more minutes than Pipe A to fill the cistern, then time in which A and B can fill the cistern separately will be respectively?
A. 15 minutes, 20 Minutes. B. 15 minutes, 10 Minutes. C. 12 minutes, 7 minutes. D. 25 minutes, 20 minutes. E. 10 minutes, 15 minutes. Supposing pipe A takes 'x' minutes and pipe 'B' takes y minutes, then A and B together will take x*y/(x+y) minutes. By supposition, x*y = 6(x+y) Plugging in values, we get option E (Note option B is wrong because the values are given in the revers order) Reason used to eliminate B is the same one used to eliminate C and D as well.



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Re: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe [#permalink]
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13 Apr 2017, 00:06
Let's do it without equations. It is clear how B,C and D were eliminated. Now we know that both pipes toghether fill the cistern in 6 minutes, so they fill 10 cisterns in an hour. Let's go to answers: A) 15 and 20 minutes mean pipe A can fill 4 cisterns and B 3 cisterns in an hour. 7 cisterns toghether<10 E) 10 and 15 minutes mean 6 and 4 cisterns per hour or 10 toghether. E indeed.



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Re: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe [#permalink]
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16 Jan 2018, 10:26
Pipe A can fill an empty water tank in 3 hours while pipe B can fill the same tank in 6 hours. When the tank is full it can be emptied by pipe C in 8 hours. Pipe A and B are opened at the same time when the tank is empty. If one hour late, pipe C is opened find the total time taken to fill the tank.
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Re: Pipe A and B running together can fill a cistern in 6 minutes. If Pipe
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