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# In a certain city, the ratio of the number of people who

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Manager
Joined: 12 Sep 2005
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In a certain city, the ratio of the number of people who [#permalink]  23 Jul 2006, 09:02
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In a certain city, the ratio of the 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- Twenty-seven percent of the population purchases neither newspaper X nor newspaper Y.

2- Seventy percent of the people who purchase newspaper Y also purchase newspaper X.
VP
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Re: DS: Interesting & diffcult maybe [#permalink]  23 Jul 2006, 10:56
C.

1. is not sufficient to get the total popn.
2. is also not suff.

from 1 and 2,

x/y = 7
x=7y

nither = 0.27
either (x+y) = 0.73
both = 0.07y

so total = x+y-xy+nither
1 = 7y + y - (0.07y) + 0.23
7.3 y = 0.73
y = 1/10
Director
Joined: 28 Dec 2005
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Re: DS: Interesting & diffcult maybe [#permalink]  23 Jul 2006, 13:07
Zagros wrote:
In a certain city, the ratio of the 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- Twenty-seven percent of the population purchases neither newspaper X nor newspaper Y.

2- Seventy percent of the people who purchase newspaper Y also purchase newspaper X.

The answer can only be C

U = a + b + neither -ab

From 1, we can find a+b and none in terms of U, but we don't know ab. insuff.
From 2, we can fine ab but we can't find the rest.

Combining both of the above, we have a solution
Senior Manager
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Re: DS: Interesting & diffcult maybe [#permalink]  23 Jul 2006, 13:24
Zagros wrote:
In a certain city, the ratio of the 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- Twenty-seven percent of the population purchases neither newspaper X nor newspaper Y.

2- Seventy percent of the people who purchase newspaper Y also purchase newspaper X.

1. intersection is not known Insuff
2. Total is not known - Insuff. (note 7:1 is only for readers - rest watch Jon stewart show -how many ----donno 7:1 is not readers and non readers)

Total and intersection known - C
SVP
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Re: DS: Interesting & diffcult maybe [#permalink]  26 Jul 2006, 01:30
MA wrote:
C.

1. is not sufficient to get the total popn.
2. is also not suff.

from 1 and 2,

x/y = 7
x=7y

nither = 0.27
either (x+y) = 0.73
both = 0.07y

so total = x+y-xy+nither
1 = 7y + y - (0.07y) + 0.23
7.3 y = 0.73
y = 1/10

One question ------- The question asks what percent of population purchases newspaper X? Not what percent of population purchase only newspaper X?

The y in the bold part is the part which purchase only newspaper Y not representative of the population that buys Y also X. Technically this part also buys Y right?
Intern
Joined: 21 Jul 2006
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Re: DS: Interesting & diffcult maybe [#permalink]  26 Jul 2006, 02:00
jaynayak wrote:
MA wrote:
C.

1. is not sufficient to get the total popn.
2. is also not suff.

from 1 and 2,

x/y = 7
x=7y

nither = 0.27
either (x+y) = 0.73
both = 0.07y

so total = x+y-xy+nither
1 = 7y + y - (0.07y) + 0.23
7.3 y = 0.73
y = 1/10

One question ------- The question asks what percent of population purchases newspaper X? Not what percent of population purchase only newspaper X?

The y in the bold part is the part which purchase only newspaper Y not representative of the population that buys Y also X. Technically this part also buys Y right?

HERE AS Y is found... we can find any other value.. since we expressed the whole population with Ys;
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Re: DS: Interesting & diffcult maybe   [#permalink] 26 Jul 2006, 02:00
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