A contractor combined x tons of a gravel mixture that : DS Archive
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# A contractor combined x tons of a gravel mixture that

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Director
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A contractor combined x tons of a gravel mixture that [#permalink]

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21 Mar 2006, 08:54
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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

Manager
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21 Mar 2006, 09:26
A

.1x + .02y = .05z
z=x+y

stmt 1 gives the value of y.
So we can calculate x

stmt2
z= x+y =16
We have no way to find x and y from this.

What's the OA?
Manager
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21 Mar 2006, 12:07
Statement 1
I used this formula:
vm=[(v1*n1)+(v2*n2)] / (n1+n2)
vm=[(0,1*n1)+(0,02*n2)] / (n1+n2)

When you know n2 (in this case y), you can easily find out n1 (in this case x).

Statement 2
0,1x+0,02y=0,05z

You know only that z=16, which is not enough to solve this.

I think the answer should be (A)
Director
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21 Mar 2006, 18:59
for st. 2 --->

x + y = 16

so y = 16-x

.10x + .02y = .05z

so, .10x + .02 (16-x) = .05*16
Solve for x..

What did i do wrong??
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21 Mar 2006, 19:14
D.

Both are SUFF...stem gives ratio of x to y.
I. Gives y, can find x.
II. Give x+y=16..use along with the ratio to find x and y...SUFF.
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21 Mar 2006, 19:52
Agree, D.

The stem already gives us 2 equations:

.1x + .02y = .05z
z=x+y

Since we have 3 variables, we need 3 distinct equations to solve the problem. Two equations are already given, so only one more distinct equation is needed. So either stmt 1 or 2 will do. Answer, D.
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21 Mar 2006, 20:03
But, can we assume that z = x+y?? What if some chemical reaction goes on between substances other than gravel in x and y and the resulting substance's weight goes down???
Director
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22 Mar 2006, 07:15
The OA is D. This was a GMATPrep question and the OE was not available.
22 Mar 2006, 07:15
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# A contractor combined x tons of a gravel mixture that

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