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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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This topic is locked. If you want to discuss this question please repost it in the respective forum. 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
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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 ".




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