BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Finding values .... !!!

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 857
Joined: Wed Aug 25, 2010 1:36 am
Thanked: 56 times
Followed by:15 members

Finding values .... !!!

by AIM GMAT » Tue Jan 25, 2011 11:17 pm
If x^2 + y^2 = 29 , what is the value of (x - y)^2 ?

1] xy = 10
2] x = 5


I was confused with the given OA , but actually while typing this question i realised my fault and understood why OA is so .OA after some discussions.
Thanks & Regards,
AIM GMAT
Top
Source: — Data Sufficiency |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Tue Jan 25, 2011 11:29 pm
AIM GMAT wrote:If x² + y² = 29 , what is the value of (x - y)² ?

1] xy = 10
2] x = 5
(x - y)² = (x² + 2xy + y²) = (x² + y²) + 2xy = 29 + 2xy
If we know the value of xy, we can determine the value of (x - y)².

Statement 1: Sufficient

Statement 2: x = 5
Implies, x² = 25
Hence, y² = (29 - 25) = 4 => y = ±2
Hence, xy = ±10 => 2xy = ±20

Not sufficient

The correct answer is A.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
Legendary Member
Posts: 2326
Joined: Mon Jul 28, 2008 3:54 am
Thanked: 173 times
Followed by:2 members
GMAT Score:710

by gmatmachoman » Tue Jan 25, 2011 11:30 pm
AIM GMAT wrote:If x^2 + y^2 = 29 , what is the value of (x - y)^2 ?

1] xy = 10
2] x = 5


I was confused with the given OA , but actually while typing this question i realised my fault and understood why OA is so .OA after some discussions.
(x - y)^2 = x^2 +Y^2 -2XY

st 1:

use the given value & substitute that.... Sufficient

St 2:

Using this u can't get "distinct" value of Yas Y can be postive or negative

Pick A
Top
Legendary Member
Posts: 857
Joined: Wed Aug 25, 2010 1:36 am
Thanked: 56 times
Followed by:15 members

by AIM GMAT » Tue Jan 25, 2011 11:55 pm
Thanks Anurag and gmatmachoman for the explanations , initially i didnt realise why st 2 cant give exact value .
Thanks & Regards,
AIM GMAT
Top
Post new topic Post Reply
• Page 1 of 1