Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 22 May 2017, 09:47

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# A contractor combined x tons of a gravel mixture that contai

 post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Director
Joined: 24 Oct 2005
Posts: 573
Location: NYC
Followers: 1

Kudos [?]: 63 [0], given: 0

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

### Show Tags

09 Apr 2006, 16:49
3
This post was
BOOKMARKED
00:00

Difficulty:

65% (hard)

Question Stats:

55% (02:13) correct 45% (01:25) wrong based on 191 sessions

### HideShow timer Statistics

A contractor combined x tons of a gravel mixture that contained 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 mixture that was 5 percent gravel G, by weight. What is the value of x ?

(1) y = 10
(2) z = 16

OPEN DISCUSSION OF THIS QUESTION IS HERE: a-contractor-combined-x-tons-of-a-gravel-mixture-that-102681.html
[Reveal] Spoiler: OA

_________________

Success is my only option, failure is not -- Eminem

VP
Joined: 29 Apr 2003
Posts: 1403
Followers: 2

Kudos [?]: 29 [0], given: 0

### Show Tags

09 Apr 2006, 16:57
C

g(x) = 10/100 * x
g(y) = 2/100 * y

g(x) + g(y) = g(z) = 5/100 * z

10x + 2y = 5z

so u need both z and y to find the value of x!
Manager
Joined: 09 Apr 2006
Posts: 173
Location: Somewhere in Wisconsin!
Followers: 1

Kudos [?]: 3 [0], given: 0

### Show Tags

09 Apr 2006, 21:42
Considering both the cases, we get the following equations:

Gravel: 10x/100 + 2y/100 = 5z/100
Non-Gravel: 90x/100 + 98y/100 = 95z/100

Case A: y = 10
=====

10x + 20 = 5z
90x + 98y = 95z

Substituting y = 10, we can solve for x = 6

Case B: z = 16
=====

10x + 2y = 80
90x + 98y = 1520

Substituting z = 16, we can solve for x = 6.

So, (A) and (B) are independently sufficient to answer the query.

So the answer is D.
_________________

Thanks,
Zooroopa

Manager
Joined: 09 Apr 2006
Posts: 173
Location: Somewhere in Wisconsin!
Followers: 1

Kudos [?]: 3 [0], given: 0

### Show Tags

10 Apr 2006, 19:21
It is quite simple. Match weights of gravel and non-gravel.

Gravel --> 10% of x + 2% of y = 5% of z
Therefore everything that remains must be non-gravel or whatever constituent is used in the mixture.

So,

Non-Gravel -->

90% of x (this is what remains from the first mixture) +
98% of y (this is what remains from the second mixture) =
95% of z (this is what remains from the third mixture)

So you get the equation that you have in bold.
_________________

Thanks,
Zooroopa

Senior Manager
Joined: 09 Aug 2005
Posts: 284
Followers: 1

Kudos [?]: 3 [0], given: 0

### Show Tags

10 Apr 2006, 20:14
how about this

n1/n2 = (c2-cm)/(cm-c1)

c1, c2 and cm are concentrations , all given

n1 = x
n2 = y = statement A

statement b gives Z , which indirectly gives y in terms of x

So D
Senior Manager
Joined: 05 Jan 2006
Posts: 382
Followers: 1

Kudos [?]: 90 [0], given: 0

### Show Tags

13 Apr 2006, 01:00
1
This post was
BOOKMARKED
D is my choice

Question gives us x+y=z and also .10x+.02y=.05z = .05(x+y)

1) gives y=10
so we can solve .10x+.02y=.05(x+y)
so sufficient

2) x+y=16 so .10x+.02y=8 ... two unique equation can solve it
so sufficient
Intern
Joined: 16 Mar 2006
Posts: 9
Location: USA
Followers: 0

Kudos [?]: 0 [0], given: 0

### Show Tags

14 Apr 2006, 10:33
Answer = B
Here is what i think
if you take total X + Y = Z (over all mass balance)
and 0.1X + 0.02 Y = 0.05 Z (Gravel balance)
We have 3 variable and two equations. But if you know the value of Z as in the second case, you can find out X and Y.
So I think Z = 16 should be sufficient to solve the equations.
_________________

"There is nothing as purifying as knowledge"

Director
Joined: 04 Jan 2006
Posts: 922
Followers: 1

Kudos [?]: 35 [0], given: 0

### Show Tags

16 Apr 2006, 12:35
I learnt a nice way of solving mixtures today and learnt that best to rewrite the problem..

So question is: x/10 + y/50 = 5/100(x+y)
z = x+y given.

1. y = 10, subs y, you get x. Suff.. So now down to A or D.
2. z = 16, so y = 16-x, subs in the question, you get X. so suff.

Hence D...

Hopefully this helps to a lot of us.. Under time pressure to get this right is whole another thing!
Intern
Joined: 11 Aug 2013
Posts: 5
Followers: 0

Kudos [?]: 1 [0], given: 0

Re: [#permalink]

### Show Tags

28 Aug 2013, 04:42
Zooroopa wrote:
Considering both the cases, we get the following equations:

Gravel: 10x/100 + 2y/100 = 5z/100
Non-Gravel: 90x/100 + 98y/100 = 95z/100

Case A: y = 10
=====

10x + 20 = 5z
90x + 98y = 95z

Substituting y = 10, we can solve for x = 6

Case B: z = 16
=====

10x + 2y = 80
90x + 98y = 1520

Substituting z = 16, we can solve for x = 6.

So, (A) and (B) are independently sufficient to answer the query.

So the answer is D.

Ohhh this is crazy...
that means you need to guess, that there is also non gravel equation suppose to be.
Math Expert
Joined: 02 Sep 2009
Posts: 38796
Followers: 7712

Kudos [?]: 105738 [1] , given: 11578

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

### Show Tags

28 Aug 2013, 09:39
1
This post received
KUDOS
Expert's post
A contractor combined x tons of a gravel mixture that contained 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 mixture that was 5 percent gravel G, by weight. What is the value of x ?

Set the equation: $$0.1x+0.02y=0.05(x+y)$$, where $$x+y=z$$ --> $$5x=3y$$ --> Q: $$x=?$$

(1) $$y=10$$ --> $$5x=3y=30$$ --> $$x=6$$. Sufficient.

(2) $$z=x+y=16$$ --> $$y=16-x$$ --> $$5x=3y=3(16-x)$$ --> $$x=6$$. Sufficient.

Answer: D.

OPEN DISCUSSION OF THIS QUESTION IS HERE: a-contractor-combined-x-tons-of-a-gravel-mixture-that-102681.html
_________________
Re: A contractor combined x tons of a gravel mixture that contai   [#permalink] 28 Aug 2013, 09:39
Similar topics Replies Last post
Similar
Topics:
6 Solution X, which is 10% alcohol is combined 2 30 Sep 2016, 10:42
A contractor combined "x" tons of a gravel mixture that 3 14 Dec 2011, 11:40
111 A contractor combined x tons of a gravel mixture that 27 28 Jan 2017, 15:44
2 A contractor combined x tons of a gravel mixture that contained 10 per 5 25 Aug 2015, 23:44
7 A contractor combined x tons of gravel mixture that cotained 10 05 Jan 2016, 13:58
Display posts from previous: Sort by

# A contractor combined x tons of a gravel mixture that contai

 post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group and phpBB SEO Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.