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# A contractor combined x tons of gravel mixture that cotained

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CEO
Joined: 29 Mar 2007
Posts: 2553

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

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17 Oct 2007, 19:39
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67% (00:55) correct 33% (00:46) wrong based on 152 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?

1) y=10
2) z=16

TOPIC LOCKED. REFER TO a-contractor-combined-x-tons-of-a-gravel-mixture-that-102681.html FOR OPEN DISCUSSION OF THE TOPIC.

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

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17 Oct 2007, 19:41
Here is what i wrote down, but I don't think its the right way to do this. I really bad at mixture probs.

x+y=z

.10x+.02y=.05z

Knowng the value of X,Y, or Z, we can solve for any of the variables this problem given the equations above.

I get D this way, but again i dunno if its just coincidence.

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

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18 Oct 2007, 09:35
Your approach looks right to me.

This note is for Killersquirrel....

Killersquirrel, can you solve this problem using your approach? I could not solve it that way.

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Manager
Joined: 02 Feb 2007
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Re: A contractor combined x tons of gravel mixture that cotained [#permalink]

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18 Oct 2007, 12:01
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?

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

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18 Oct 2007, 13:35
2
KUDOS
see attachment:

The new ratio is 3:5

statement 1

when you know that Y=10 then

10/X = 5/3

30 = 5X

6 = X

sufficient

statement 2

since Z = 16 and you know that 16/(5+3) = 2 then X=3*2 Y=5*2

sufficient

the answer is (D)
Attachments

untitled.JPG [ 7.19 KiB | Viewed 5722 times ]

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

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18 Oct 2007, 15:41
KillerSquirrel wrote:
see attachment:

The new ratio is 3:5

statement 1

when you know that Y=10 then

10/X = 5/3

30 = 5X

6 = X

sufficient

statement 2

since Z = 16 and you know that 16/(5+3) = 2 then X=3*2 Y=5*2

sufficient

the answer is (D)

Hey, KS...would you mind explaining this a little further?

Thanks!

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GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5032

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

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18 Oct 2007, 18:37
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)
....

So only one set works, x = 6, y = 10. Sufficient.

Ans D

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

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15 Aug 2009, 20:04
I was lost without you ywilfred !!
_________________

http://gmatclub.com/forum/countdown-beginshas-ended-85483-40.html#p649902

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Manager
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Location: Denver, CO
WE 1: IT Business Analyst-Building Materials Industry
Re: A contractor combined x tons of gravel mixture that cotained [#permalink]

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17 Feb 2010, 17:57
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?

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Manager
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Location: India
Concentration: Operations, General Management
Schools: IIMA (M)
GMAT 1: 640 Q48 V29
GMAT 2: 670 Q49 V31
WE: Supply Chain Management (Military & Defense)
Re: A contractor combined x tons of gravel mixture that cotained [#permalink]

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22 Apr 2011, 23:51

there is a similar question on forum in mixture prob
_________________

lets start again

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

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05 Jan 2016, 13:58
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Re: A contractor combined x tons of gravel mixture that cotained   [#permalink] 05 Jan 2016, 13:58
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# A contractor combined x tons of gravel mixture that cotained

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