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

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17 Oct 2007, 18:39

6

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00:00

A

B

C

D

E

Difficulty:

(N/A)

Question Stats:

65% (01:52) correct
35% (00:46) wrong based on 124 sessions

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A contractor combined x tons of gravel mixture that cotained 10 percent gravel G, by weight, with y tons of a mixture that contained 2 percent gravel G, by weight, to produce z tons of a misture that was 5 percent gravel G, by weight. What is the value of X?

Re: A contractor combined x tons of gravel mixture that cotained [#permalink]

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18 Oct 2007, 11:01

hey guys, i got D also, but my approach was a bit different, call it old fashion if you'd like.

I figured from the problem that x=10% gravel (G) y=2%G, and Z=5%G
we know that z=x+y

if we know x=10, therefore 10=10%G, so we find out how much gravel is in the mixture. After we find G, z=5%G, and it proves suff. Same goes for y, also suff, becasue we can find the gravel from it.

How do you guys feel about this approach? Is it dangerous to think it that way?

Re: A contractor combined x tons of gravel mixture that cotained [#permalink]

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18 Oct 2007, 17:37

z/20 = x/10 + y/50
5z = 10x + 2y
Since z = x+y,
5x + 5y = 10x+2y
x = 3y/5

St1:
y = 10. Sufficient. Can solve for x.

St2:
z = 16.

5z = 10x+2y
80 = 10x + 2y

Possible sets:
x = 7, y = 5 (x+y = 12. Out)
x = 6, y = 10 (x+y = 16. In)
x = 5, y = 15 (x+y = 20. Out)
x = 4, y = 20 (x+y = 24. Out)
x = 3, y = 25 (x+y = 28. Out)
....

Re: A contractor combined x tons of gravel mixture that cotained [#permalink]

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17 Feb 2010, 16:57

I have to give kudos to Killer Squirrel for posting his approach. I am not a math person so the algebraic method makes no sense to me. KS's approach is helping me destroy these problems. Just one questing is there any limitations to this approach?

Re: A contractor combined x tons of gravel mixture that cotained [#permalink]

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05 Jan 2016, 12:58

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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