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Last year, if Elena spent a total of $720 on newspapers, mag

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Last year, if Elena spent a total of $720 on newspapers, mag  [#permalink]

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New post 13 Jan 2014, 01:54
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The Official Guide For GMAT® Quantitative Review, 2ND Edition

Last year, if Elena spent a total of $720 on newspapers, magazines, and books, what amount did she spend on newspapers?

(1) Last year, the amount that Elena spent on magazines was 80 percent of the amount that she spent on books.
(2) Last year, the amount that Elena spent on newspapers was 60 percent of the total amount that she spent on magazines and books.

Data Sufficiency
Question: 33
Category: Arithmetic Percents
Page: 155
Difficulty: 600


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Re: Last year, if Elena spent a total of $720 on newspapers, mag  [#permalink]

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New post 13 Jan 2014, 01:55
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SOLUTION:

Last year, if Elena spent a total of $720 on newspapers, magazines, and books, what amount did she spend on newspapers?

Given that \(n + m + b = 720\), find the value of n.

(1) Last year, the amount that Elena spent on magazines was 80 percent of the amount that she spent on books --> \(m=0.8b\) --> \(n + 0.8b + b = 720\) --> \(n=720-\frac{9}{5}b\). Not sufficient.

(2) Last year, the amount that Elena spent on newspapers was 60 percent of the total amount that she spent on magazines and books --> \(n=0.6(m+b)\) --> \(\frac{5}{3}n=m+b\) --> substitute: \(n + m + b =n+\frac{5}{3}n =720\) --> we can solve for n. Sufficient.

Answer: B.
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Re: Last year, if Elena spent a total of $720 on newspapers, mag  [#permalink]

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New post 13 Jan 2014, 22:54
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Last year, if Elena spent a total of $720 on newspapers, magazines, and books, what amount did she spend on newspapers?

(1) Last year, the amount that Elena spent on magazines was 80 percent of the amount that she spent on books.
(2) Last year, the amount that Elena spent on newspapers was 60 percent of the total amount that she spent on magazines and books.

Data Sufficiency
Question: 33
Category: Arithmetic Percents
Page: 155
Difficulty: 600


My Solution:
From Question: N(newspapers) + M (magazines) + B(books) = 720
From (1) : M =80/100(B)
M= 4/5B

Subs in Question: N+ 4/5B+B = 720 ( Two unknown values), So insufficient.
From(2): N=60/100(M+B)
N=3/5(M+B)
Since we need to find N, Keeping N in the equation. So M=5/3N-B
Subs in Main equation: N+ 5/3N-B +B= 720
N+5/3N= 720
So, can find N... Sufficient! My ANSWER : B
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Re: Last year, if Elena spent a total of $720 on newspapers, mag  [#permalink]

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New post 14 Jan 2014, 11:58
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Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND Edition

Last year, if Elena spent a total of $720 on newspapers, magazines, and books, what amount did she spend on newspapers?

(1) Last year, the amount that Elena spent on magazines was 80 percent of the amount that she spent on books.
(2) Last year, the amount that Elena spent on newspapers was 60 percent of the total amount that she spent on magazines and books.



Statement 1) magazine = .8 of books. As newspaper expenditure is not provided. Hence Not sufficient.

Statement 2) Lets assume magazine expenditure = m, newspaper expenditure = n and book expenditure = b
then n = 0.6(m+b)
we know that m+n+b = $720
=> 1.6 (m+b) = $720
We can find out the value of (m+b) and from there we can find the value of n as well.
hence Option B)
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Re: Last year, if Elena spent a total of $720 on newspapers, mag  [#permalink]

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New post 04 Aug 2017, 17:54
In regards to st2, is it the same as saying N = 60 % of 720 and M+B = 40% of 720?
We can't figure out exact values for M and B, but we can for M+B

Just so I have a better understanding for these types of questions

Thanks

kinjiGC wrote:
Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND Edition

Last year, if Elena spent a total of $720 on newspapers, magazines, and books, what amount did she spend on newspapers?

(1) Last year, the amount that Elena spent on magazines was 80 percent of the amount that she spent on books.
(2) Last year, the amount that Elena spent on newspapers was 60 percent of the total amount that she spent on magazines and books.



Statement 1) magazine = .8 of books. As newspaper expenditure is not provided. Hence Not sufficient.

Statement 2) Lets assume magazine expenditure = m, newspaper expenditure = n and book expenditure = b
then n = 0.6(m+b)
we know that m+n+b = $720
=> 1.6 (m+b) = $720
We can find out the value of (m+b) and from there we can find the value of n as well.
hence Option B)
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Re: Last year, if Elena spent a total of $720 on newspapers, mag  [#permalink]

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Re: Last year, if Elena spent a total of $720 on newspapers, mag   [#permalink] 24 Nov 2018, 20:14
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