Announcement, 9/22/08: Beat The GMAT is thrilled to welcome Clear Admit and Accepted.com to our community!

GMATPrep equation problem


 
Post new topic   Reply to topic    Beat The GMAT Forum Index -> GMAT Math -> Data Sufficiency
View previous topic :: View next topic  
Author Message
netigen
GMAT Destroyer!


Joined: 19 Feb 2008
Posts: 633

Thanks given: 3
Thanked 23 times in 23 posts
PostPosted: Mon May 12, 2008 2:15 am    Post subject: GMATPrep equation problem Reply with quote
Help me get this one right.

I thought we can solve for XY using both the equations if we subtract one equation from another we get

x^2 = x or x=1 and hence, y=2

OA is E
This post contains an attachment. You must be logged in to download/view this file.
Please login or register as a user.
Back to top


View user's profile Send private message
amitansu
Really wants to Beat The GMAT!


Joined: 26 Feb 2008
Posts: 293

Thanks given: 0
Thanked 8 times in 8 posts


Target GMAT Score: 750
PostPosted: Mon May 12, 2008 2:19 am    Post subject: Reply with quote
Netigen, you are right.
Ans should be C.


Amit
Back to top


View user's profile Send private message
akshatsingh
Rising GMAT Star


Joined: 10 Apr 2008
Posts: 77

Thanks given: 0
Thanked 3 times in 3 posts
PostPosted: Mon May 12, 2008 10:03 pm    Post subject: Reply with quote
x^2 = x doesnt mean x = 1.

it means x(x-1) = 0
=> x=0 or x=1

Clearly a unique xy cannot be found out using these values of x.


I believe answer should be E.
_________________
Aks
Back to top


View user's profile Send private message
netigen
GMAT Destroyer!


Joined: 19 Feb 2008
Posts: 633

Thanks given: 3
Thanked 23 times in 23 posts
PostPosted: Mon May 12, 2008 10:39 pm    Post subject: Reply with quote
I knew I was doing something stupid Cool, thanks for pointing it out.
Back to top


View user's profile Send private message
gabriel
Managing Director


Joined: 20 Dec 2006
Posts: 841

Thanks given: 115
Thanked 27 times in 26 posts

Location: India
PostPosted: Tue May 13, 2008 12:28 pm    Post subject: Reply with quote
akshatsingh wrote:
x^2 = x doesnt mean x = 1.

it means x(x-1) = 0
=> x=0 or x=1

Clearly a unique xy cannot be found out using these values of x.


I believe answer should be E.


This is a very common mistake committed in DS. We have to remember any quadratic equation will have 2 roots. So never ever stop after you find one value for x if there is a term x^2 in the equation.

Regards
Back to top


View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Beat The GMAT Forum Index -> GMAT Math -> Data Sufficiency All times are GMT - 7 Hours
Page 1 of 1

 
Jump to:  
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.