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Gmat Prep - Mixture

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Gmat Prep - Mixture

by mttorii » Sun Jul 06, 2008 2:55 pm
Can someone help me how to struture this question?

A contractor combined X tons of a gravel mixture that contained 10% gravel G, by weight, with Y tons of a mixture that contained 2% gravel G, by weight, to produce Z tons of a mixture that was 5% gravel G, by weight. What is the value of X?

(1) Y = 10
(2) Z = 16

tks
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Source: — Data Sufficiency |
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by ed09 » Sun Jul 06, 2008 6:19 pm
Hi mttorii,

My solution is:

First, rewrite the problem clause in an equation.
0,1x+0,02y=0,05(x+y)

Than
(1) y=10
substitute y in the eqation
0,1x+0,02*10=0,05(x+10)
This is one equation with one unknown. That is, we can solve for x.
SUFFICIENT

(2) z=16
Because the mixture contains gravel x and gravel Y ONLY, z=x+y.
So we have the following system of two equations with two unknowns
0,1x+0,02y=0,05(x+y) and
x+y=16
That is, we can solve this system for x and y.
SUFFICIENT

In both cases we have that x=6 and y=10.

The answer is D, isn't it?

Best!
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by mttorii » Mon Jul 07, 2008 2:52 am
Hi Ed09

Yes, D is the answer. Very didatic!
Thank you.
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OA is D

by ektamatta » Fri Jul 11, 2008 7:27 pm
There is another way to look over this problem

when have given X tons = 10% of G
Y tons = 2% of G
Z tons = 5% of G

In the first statement we have given the value of Y. plugging in the value of Y we can find the G therefore after getting the value of G we can find the value of X

Same logic applies to statement II

So both the equation is sufficient . hence OA is 'D'
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