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At their respective rates, pump A, B, and C can fulfill an
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29 Jul 2008, 10:22
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At their respective rates, pump A, B, and C can fulfill an empty tank, or pumpout the full tank in 2, 3, and 6 hours. If A and B are used to pumpout water from the halffull tank, while C is used to fill water into the tank, in how many hours, the tank will be empty? A. 2/3 B. 1 C. 3/4 D. 3/2 E. 2 == Message from GMAT Club Team == This is not a quality discussion. It has been retired. If you would like to discuss this question please repost it in the respective forum. Thank you! To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative  Verbal Please note  we may remove posts that do not follow our posting guidelines. Thank you.



Senior Manager
Joined: 14 Mar 2007
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Re: work and time PS
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29 Jul 2008, 10:30
my answer is C.
I can explain if it is correct.



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Joined: 14 Mar 2007
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Re: work and time PS
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29 Jul 2008, 10:31
my answer is C.
I can explain if it is correct.



Senior Manager
Joined: 23 May 2006
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Re: work and time PS
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29 Jul 2008, 17:22
arjtryarjtry wrote: At their respective rates, pump A, B, and C can fulfill an empty tank, or pumpout the full tank in 2, 3, and 6 hours. If A and B are used to pumpout water from the halffull tank, while C is used to fill water into the tank, in how many hours, the tank will be empty? A. 2/3 B. 1 C. 3/4 D. 3/2 E. 2 Since the tank is already half full you have 2/x instead of 1/x; and always substract the small quantity from the large one. Hence in this case water out > in water 2/x = (1/2+1/3)  1/6 2/x = 4/6 we need to find out in how many hours will the tank be empty that was already half full so x/2 x/2 = 6/4 = 3/2 IMO D



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Joined: 17 Jun 2008
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Re: work and time PS
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03 Aug 2008, 11:41
arjtryarjtry wrote: At their respective rates, pump A, B, and C can fulfill an empty tank, or pumpout the full tank in 2, 3, and 6 hours. If A and B are used to pumpout water from the halffull tank, while C is used to fill water into the tank, in how many hours, the tank will be empty? A. 2/3 B. 1 C. 3/4 D. 3/2 E. 2 Lets take work done in one hr: Wa=t/2 Wb=t/3 Wc=t/6 where t=total tank capacity now in 1 hr if C fills and A,B empty the tank effective workdone woll be Wa+Wb  Wc = t/2 +t/3 t/6 =4t/6=2t/3 => to empty complete tank t/2t/3 =3/2 hrs are required IMO D
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Director
Joined: 23 Sep 2007
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Re: work and time PS
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03 Aug 2008, 13:00
C
pump A & B together can empty 5/6 of the tank in 1 hour, or half the tank in 3/5 hour (36 minutes). During 3/5 hour, pump C fills 3/30 of the tank, which causes pump A & B to spend another 6.5 minutes to empty, during this 6.5 minutes ....



Current Student
Joined: 11 May 2008
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Re: work and time PS
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03 Aug 2008, 19:00
net effect of all these JOBLESS guys working together in 1 hr=1/6(fill)(1/2+1/3)(empty)=2/3 WHAT DOES THIS 2/3 MEAN??? it means that in if these guys work together 1 hr,then the net work done is ve or there is net emptying of the tank. so the work this probelm gives us is 1/2( means that 1/2 of work should be done and ve means that net effect should be emptying) so , no. of hrs=(1/2)/(2/3). this is same as saying if u have to go 100kms and your rate is 50kmph, then u compelte in 100/50=2hrs. =3/4. i finished 1 full bottle in the last 1/2 hr .. so i hope this ans is ok. otherwise , i pray for forgiveness



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Joined: 18 Jul 2008
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Re: work and time PS
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05 Aug 2008, 16:20
Is there an alternate explanation? Not quite sure if I complete follow what was given above. Thanks.



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Re: work and time PS
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05 Aug 2008, 16:56
Oops i didnt notice half filled silly mistake even i get 3/4 hrs option C I opted following method : say t is the capacity of tank A to empty the tank in 1 hr : t/2 B to empty the tank in 1 hr : t/3 C to empty the tank in 1 hr: t/6 now effective work done for 1 hr if C were to fill the tank,A,B were to empty the tank : t/2 + t/3 t/6=4t/6=2t/3 hence time taken to empty half filled tank : t/2 / 2t/3 =3/4 hrs == Message from GMAT Club Team == This is not a quality discussion. It has been retired. If you would like to discuss this question please repost it in the respective forum. Thank you! To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative  Verbal Please note  we may remove posts that do not follow our posting guidelines. Thank you.
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Re: work and time PS &nbs
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05 Aug 2008, 16:56






