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# M24 #4

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Manager
Joined: 18 Jan 2012
Posts: 51
Location: United States

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03 Jul 2012, 00:19
Dce25 wrote:
Let the amount of acid in 80 gram solution(acid+water) be m grams:
So concentration= [m][/80]

So new conc. = [m][/80+x]

Now Acc. to question [m][/80+x] = [1][/y] of [m][/80]

Solving we get: 80y = 80+x

Therefore each statement is sufficient.

I believe that you have made incorrect inferences. The question stem ask about figuring out the original concentration of the acid. In other words, you have to figure out m.
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Manager
Joined: 18 Jan 2012
Posts: 51
Location: United States

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03 Jul 2012, 00:24
Dce25 wrote:
Let the amount of acid in 80 gram solution(acid+water) be m grams:
So concentration= [m][/80]

So new conc. = [m][/80+x]

Now Acc. to question [m][/80+x] = [1][/y] of [m][/80]

Solving we get: 80y = 80+x

Therefore each statement is sufficient.

In Data sufficiency questions, its is exceptionally important to remain focused on what is being asked. AS per the question stem, What was the concentration of acid in the original solution?.
In other words, as per the variables that you have used, one is asked to figure out m/80.
Knowledge of "x" and "y" doesn't help us in achieving this objective
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Manager
Joined: 14 Jun 2012
Posts: 65

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31 Aug 2012, 20:23
Took the approach of setting up equations and then substituting the given values. Either statement individually is not sufficient since there are 2 variables X and Y.

Considering both the statements together, we get

Total weight of the new solution = 80+X = 80+80 =160

New concentration of acid = (1/Y) = 1/2

Since initial concentration of neither the water nor the acid is given we will be unable to solve the equations. Eg. if initial concentration of acid was say 40 gms then new concentration will be 20 whereas if initial conc of acid was 60 then new would be 30.

Thus I chose the statement E as the answer. Took me a minute and a half though. Will work on improving my speed.
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Senior Manager
Joined: 13 Jan 2012
Posts: 307
Weight: 170lbs
GMAT 1: 740 Q48 V42
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02 Jul 2013, 09:36
Hoping that Bunuel posts an explanation soon.
Math Expert
Joined: 02 Sep 2009
Posts: 39626

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02 Jul 2013, 11:21
Hoping that Bunuel posts an explanation soon.

This question needs revision. Will edit soon.
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Re: M24 #4   [#permalink] 02 Jul 2013, 11:21

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# M24 #4

Moderator: Bunuel

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