| View previous topic :: View next topic |
| Author |
Message |
zozo123
Rising GMAT Star
Joined: 13 Feb 2007
Posts: 56
Thanks given: 0
Thanked 0 times in 0 posts
|
 Posted: Tue Jun 12, 2007 6:32 am Post subject: GMAT prep question |
 |
|
If x, y, and k are positive numbers such that (x/(x+y))(10) + (y/(x+y))(20) = k and if x < y, which of the following could be the value of k?
A. 10
B. 12
C. 15
D. 18
E. 30 |
|
| Back to top |
|
 |
|
|
f2001290
GMAT Destroyer!
Joined: 10 Mar 2007
Posts: 400
Thanks given: 0
Thanked 0 times in 0 posts
|
| Posted: Tue Jun 12, 2007 6:48 am Post subject: |
|
|
Is it D.
Given equation can be reduced to (10-k)x = (k-20)y
From here, I used back-solving. Only D satisfies the condition X<Y |
|
| Back to top |
|
|
jayhawk2001
Moderator
Joined: 28 Jan 2007
Posts: 789
Thanks given: 0
Thanked 11 times in 11 posts
Location: Silicon valley, California
|
| Posted: Tue Jun 12, 2007 8:48 pm Post subject: Re: GMAT prep question |
|
|
| zozo123 wrote: | If x, y, and k are positive numbers such that (x/(x+y))(10) + (y/(x+y))(20) = k and if x < y, which of the following could be the value of k?
A. 10
B. 12
C. 15
D. 18
E. 30 |
The eqn can be reduced to
(10x + 20y) / (x+y) = k
10 + 10y/(x+y) = k
y / (x+y) will be > 0 and < 1 as we know x and y are positive. So,
discard A and E.
When x = y, y/(x+y) = 1/2 and when x = 0, y/(x+y) = 1. So, value of
y/(x+y) will vary between 1/2 and 1. So, discard B and C.
Only D remains. |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum
|
|
"GMAT" and other GMAC™ trademarks are registered trademarks of the Graduate Management Admission Council™. The Graduate Management Admission Council™ does not endorse, nor is it affiliated in any way with the owner or any content on this website. The opinions expressed here are solely those of the author or those of the members of this website. Copyright © 2008 BTG Test Prep, LLC. Powered by phpBB © 2001, 2005 phpBB Group.
|
|
