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DS: Pool Y and Pool X [#permalink]
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07 Dec 2010, 08:21
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33% (01:12) wrong based on 482 sessions
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If Pool Y currently contains more water than Pool X, and if Pool X is currently filled to 2/7 of its capacity, what percent of the water currently in Pool Y needs to be transferred to Pool X if Pool X and Pool Y are to have equal volumes of water? (1) If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity. (2) Pool X has a capacity of 14,000 gallons. Hi.
I came across this DS question on my last MgCAT, and while I do understand how to solve it, I fail to see why (according to the Mg explanation) we should consider both pools capacity as equal, when nothing in the text leads to that assumption… (or am I missing something here?) Therefore I felt for E.
Thanks for the help.
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Re: Can someone clear out this DS question for me plz. [#permalink]
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07 Dec 2010, 09:10
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itnas wrote: Hi.
I came across this DS question on my last MgCAT, and while I do understand how to solve it, I fail to see why (according to the Mg explanation) we should consider both pools capacity as equal, when nothing in the text leads to that assumption… (or am I missing something here?) Therefore I felt for E.
Thanks for the help.
If Pool Y currently contains more water than Pool X, and if Pool X is currently filled to 2/7 of its capacity, what percent of the water currently in Pool Y needs to be transferred to Pool X if Pool X and Pool Y are to have equal volumes of water?
(1) If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity.
(2) Pool X has a capacity of 14,000 gallons. We are nowhere told that the capacities of pools X and Y are equal. (1) If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity > together pools X and Y contain 6/7 of the capacity of pool X. Now, in order pools X and Y to contain equal amount of water each pool should contain 3/7 of the capacity of pool X, thus from pool Y, which contains 4/7 (6/72/7=4/7) of the capacity of pool X we must transfer 1/7 of the capacity of pool X, which is 25% of the water currently in pool Y (1/7)/(4/7)=1/4. Sufficient. Or consider the following: Let the capacity of pool X be 7 gallons. It's 2/7 full, thus there are 2 gallons of water. If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity and thus will contain 6 gallons of water, which means that there are now 62=4 liters of water in pool Y (it doesn't matter what capacity it has). In order both pools to contain equal amount of water each pool should contain 3 gallons of water, thus we should transfer 1 gallon from pool Y to pool X. 1 gallon is 1/4 of the water currently in pool Y. (2) Pool X has a capacity of 14,000 gallons. No info about pool Y. Not sufficient. Answer: A. Hope it's clear.
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Re: Can someone clear out this DS question for me plz. [#permalink]
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07 Dec 2010, 09:22
Thanks, I guess I just got blinded by not knowing the capacity of either pools. Your explanations just remind me the scene of Die Hard 3 when transferring gallons of water from one “jar” to another in order to disarm the bomb



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Re: Can someone clear out this DS question for me plz. [#permalink]
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07 Dec 2010, 20:36
Haha! I started reading the question and thought of the same thing... ahhhh the 90s action movies



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Re: Pool Capacity [#permalink]
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18 Sep 2011, 15:55
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Lets say pool x's total capacity = x => Pool x filled capacity = (2/7)x
Lets say pool y's total capacity = y
lets say pool y's filled capacity = py ( where p is some fraction)
Let r be the volume transferred from y to x.
if py  r = (2/7)x+r , r is what percent of py?
1. Sufficient
py r = (2/7)x+r = (6/7)x
(2/7)x+r = (6/7)x => r = (4/7)x
py  r = (6/7)x => py = (10/7)x
r is what percent of py? i.e is (((4/7)x) / ((10/7)x)) *100
= (4/10)*100
2. Not sufficient we dont know anything about pool y or how much removed from pool y.
Answer is A.



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Re: If Pool Y currently contains more water than Pool X, and if [#permalink]
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24 Jun 2013, 03:17



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Re: If Pool Y currently contains more water than Pool X, and if [#permalink]
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24 Jun 2013, 11:33
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Bunuel wrote: Bumping for review and further discussion*. Get a kudos point for an alternative solution! *New project from GMAT Club!!! Check HEREQuestion: Let the capacity of X be C so, X= 2C/7 and Y>X If n is the quantity of water taken from Y and put into X Then, Yn = X+n 2n = YX => n = (YX)/2 n is the quantity that needs to be transferred. The % will (n/Y) * 100 % (Note, that we already have one equation with X and C, and we just need one more involving Y and C, if we can get it out of any of the statements, it should be enough to solve) Now lets take a look at the statements : (1) If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity. Y+X = 6C/7 and we know that X=2C/7 Hence, Y=4C/7 n = (YX)/2 = C/7 Therefore, % of water = (C/7)/(4C/7) *100 =100/4 =25% Sufficient. (2) Pool X has a capacity of 14,000 gallons. We need another relation in Y and C or Y and X to be able to solve, not sufficient. Ans: A
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Re: If Pool Y currently contains more water than Pool X, and if [#permalink]
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Re: If Pool Y currently contains more water than Pool X, and if [#permalink]
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15 Jan 2016, 03:21
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
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Re: If Pool Y currently contains more water than Pool X, and if [#permalink]
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19 Feb 2017, 09:27
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
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Re: If Pool Y currently contains more water than Pool X, and if
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