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Ratio Problem

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johanna.j.farrell
 Post subject: Ratio Problem
 Post Posted: Tue Sep 28, 2010 1:46 pm 
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Students


Posts: 2
Can someone please explain how to solve this problem? The picture doesn't copy but the question can be found in the quantitative tutorial titled: The Many Ways the GMAT Tests Ratios. Please help!!

What is the value of p if if rq is not equal to 0?

(1) r = 4
(2) q = 3r

Thanks!!!
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gokul_nair1984
 Post subject: Re: Ratio Problem
 Post Posted: Tue Sep 28, 2010 4:03 pm 
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Stem: p=(3/r)/[(2/q)+(3/2q)] and rq is not equal to 0. What is p?

(1) r = 4
(2) q = 3r

The Stem can be simplified to p=6q/7r or p=(6/7)*(q/r)

From Statement 1, we do not get the value of p because we need the value of q along with the value of r, which is given.

From Statement 2, we know that (q/r)=3. Substituting this value in the stem , we can find a unique value for p , hence B is sufficient
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johanna.j.farrell
 Post subject: Re: Ratio Problem
 Post Posted: Wed Sep 29, 2010 12:20 am 
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Could you please walk me through how you simplified the expression? I am having trouble understanding how you got p=(6/7)*(q/r).

Thanks!
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gokul_nair1984
 Post subject: Re: Ratio Problem
 Post Posted: Wed Sep 29, 2010 3:38 am 
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johanna.j.farrell wrote:
Could you please walk me through how you simplified the expression? I am having trouble understanding how you got p=(6/7)*(q/r).


p=(3/r)/[(2/q)+(3/2q)]

Don't get flabbergasted by such terms, instead solve them individually by breaking them down

Consider this to be a/b, where a=(3/r) and b=(2/q)+(3/2q).

a/b can also be written as a*(1/b)

Let's first solve , b=(2/q)+(3/2q). LCM is 2q. Therefore, b can be reduced to [(2*2)+(3)]/2q=7/2q and (1/b)=2q/7--The reciprocal of b.

a=3/r.

Therefore, a*(1/b)=(3/r) * (2q/7)= 6q/7r= (6/7) * (q/r)

Is it clear now?
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tim
 Post subject: Re: Ratio Problem
 Post Posted: Thu Oct 07, 2010 8:37 pm 
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ManhattanGMAT Staff


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Location: Southwest Airlines, seat 21C
thanks Gokul. Johanna, let us know if you still have any questions..

_________________
Tim Sanders
Manhattan GMAT Instructor
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