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In a certain city, the ratio of number of people who [#permalink]
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25 Oct 2008, 09:19
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In a certain city, the ratio of number of people who purchase newspaper X to the number of people who purchase newspaper Y is 7:1. What percent of the population purchases newspaper Y. (1) 27% of the population purchases neither newspaper X nor newspaper Y (2) 70% of the people who purchase newspaper Y also purchase newspaper X == 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: DS : Kaplan : Percentages [#permalink]
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25 Oct 2008, 13:14
amitdgr wrote: In a certain city, the ratio of number of people who purchase newspaper X to the number of people who purchase newspaper Y is 7:1. What percent of the population purchases newspaper Y.
(1) 27% of the population purchases neither newspaper X nor newspaper Y (2) 70% of the people who purchase newspaper Y also purchase newspaper X A x:y :: 7:1 1. 73% will buy either x or yor both  This is where I feel I could be making the mistake 8a = 73% a = 9.1% Y = 9.1%  Sufficeint 2. In Suff



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Re: DS : Kaplan : Percentages [#permalink]
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25 Oct 2008, 13:35
amitdgr wrote: In a certain city, the ratio of number of people who purchase newspaper X to the number of people who purchase newspaper Y is 7:1. What percent of the population purchases newspaper Y.
(1) 27% of the population purchases neither newspaper X nor newspaper Y (2) 70% of the people who purchase newspaper Y also purchase newspaper X y = x , x = 7x population say = 1000 from 1 730/8.........suff from 2 insuff A



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Re: DS : Kaplan : Percentages [#permalink]
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26 Oct 2008, 00:58
Given OA is C
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Re: DS : Kaplan : Percentages [#permalink]
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26 Oct 2008, 23:15
amitdgr wrote: Given OA is C Amit, could you check if something is missing in the question posted? With the current wordings, A seems to be sufficient.



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Re: DS : Kaplan : Percentages [#permalink]
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26 Oct 2008, 23:39
attaching the screenshot. I had also picked A.
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Re: DS : Kaplan : Percentages [#permalink]
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27 Oct 2008, 01:00
Thanks Amit for the posting. Now I understand what I was overlooking. Basically, the raio of 7:1 is of numbers and from stmt1: we only know of the percentage of union. Hence, this will not be sufficient to get the desired ratio.



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Re: DS : Kaplan : Percentages [#permalink]
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27 Oct 2008, 01:08
scthakur wrote: Thanks Amit for the posting. Now I understand what I was overlooking. Basically, the raio of 7:1 is of numbers and from stmt1: we only know of the percentage of union. Hence, this will not be sufficient to get the desired ratio. how do we calculate using the 2 statements ?
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Re: DS : Kaplan : Percentages [#permalink]
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27 Oct 2008, 01:20
amitdgr wrote: scthakur wrote: Thanks Amit for the posting. Now I understand what I was overlooking. Basically, the raio of 7:1 is of numbers and from stmt1: we only know of the percentage of union. Hence, this will not be sufficient to get the desired ratio. how do we calculate using the 2 statements ? Suppose, p is the total population then from stmt1: 0.73p = XUY = X + Y + X intersection Y = 8Y + X intersection Y....insufficient. From stmt2: X intersection Y = 0.7Y. Combining two, 0.73p = 8.7Y and hence, Y/p can be determined.



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Re: DS : Kaplan : Percentages [#permalink]
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27 Oct 2008, 03:33
I found my mistake too



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Re: DS : Kaplan : Percentages [#permalink]
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25 Dec 2008, 15:34
Question stem: Let P=population X/Y = 7 Y/P=? _______________
XuY  union of X and Y X_Y  intersection of X and Y
Stmt 1: X_Y/P=0.27 Stmt 2: Y/XuY=0.7
Neither statement alone is suff. So, either C or E. P=X+YXuY+X_Y  we need to see if we can make this expression consisting of P and Y only. From stem: X=7Y; from stmt1: X_Y=0.27P from stmt2: XuY=Y/0.7 Replacing for the above we have : P = 7Y + Y Y/0.7 +0.27P; We can bring the above to Y/P form. So answer should be C. Let me know you spot any mistake.



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Re: DS : Kaplan : Percentages [#permalink]
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25 Dec 2008, 20:42
I also choose C.
Statement 1 provides us the total percentage of population who buy newspaper, that is 73% total population. but it is insufficient to conclude that in this 73%, the people buy A:B = 7:1 because many people buy B also buy A.
we put the number who buy B = X, then according to the ratio A:B = 7:1 then number buy A = 7X. So the number who buy newspaper could be X+7X subtract the number of people who buy both A and B = total 73% population
Use the statement 2, we know that 70% people buy B also buy A and we have this number equal to 0.7X. This number should be subtracted from the total.
Then we get X+7X  0.7X = 7.3X = 73% population => x =10%.
So it is C



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Re: DS : Kaplan : Percentages [#permalink]
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27 Dec 2008, 10:08
scthakur wrote: amitdgr wrote: scthakur wrote: Thanks Amit for the posting. Now I understand what I was overlooking. Basically, the raio of 7:1 is of numbers and from stmt1: we only know of the percentage of union. Hence, this will not be sufficient to get the desired ratio. how do we calculate using the 2 statements ? Suppose, p is the total population then from stmt1: 0.73p = XUY = X + Y + X intersection Y = 8Y + X intersection Y....insufficient. From stmt2: X intersection Y = 0.7Y. Combining two, 0.73p = 8.7Y and hence, Y/p can be determined. Why you put X + Y = 8Y, 8Y also include those population which buy both X & Y. SO for me you can't replace it directly.
I still think there is issue in question it self. If question is such that : Find the population which buy ONLY paper Y



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Re: DS : Kaplan : Percentages [#permalink]
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27 Dec 2008, 15:48
I concur with amitgupta that the questions should be " Y only ". == 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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