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

Redeem

Interesting GMATFix Problem-11

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Community Manager
Posts: 1048
Joined: Mon Aug 17, 2009 3:26 am
Location: India
Thanked: 51 times
Followed by:27 members
GMAT Score:670

Interesting GMATFix Problem-11

by arora007 » Tue Sep 21, 2010 12:52 pm
X^2 + bx + c = 0 has two integer solutions for the values of x. b is an integer constant and c is a prime number constant. Is |x| >2 ?
1) b is odd
2) c is even
https://www.skiponemeal.org/
https://twitter.com/skiponemeal
Few things are impossible to diligence & skill.Great works are performed not by strength,but by perseverance

pm me if you find junk/spam/abusive language, Lets keep our community clean!!
Top
Source: — Data Sufficiency |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 1179
Joined: Sun Apr 11, 2010 9:07 pm
Location: Milpitas, CA
Thanked: 447 times
Followed by:88 members

by Rahul@gurome » Tue Sep 21, 2010 11:00 pm
Solution:
Let the integer solutions of x be m , n.
So m+n = -b
and mn = c.
Since c is prime, one of m or n has to be 1 or -1 and the other has to be the prime number.
If lxl > 2, it means either x > 2 or x < -2.
So we need to know if both m, n > 2 or both m, n < -2.
Consider first (1) alone.
b is odd.
So m+n = - odd number.
Since one of m and n is 1 or -1, the other has to be even, because only even + odd gives odd.
Also it has to be prime.
The only possibility is -2 or 2.
So the only possible values of m, n are 1, -1, -2, 2.
Now l1l = 1< 2, l2l =2 ,l-1l = 1 < 2, l-2l = 2 .
So lml or lnl is not > 2.
Or lxl is not > 2
So (1) alone is sufficient to answer the question.
Next consider (2) alone.
If c is even c has to be 2 because it is given that is a prime.
Or mn is 2.
So one of m or n is 1 and the other is 2 or one of m, n is -1 and the other is -2.
Now l1l < 2, l2l = 2, l-1l = 1 < 2, l-2l = 2.
So lml or lnl is not > 2.
Or lxl is not > 2.
So (2) alone is also sufficient to answer the question.

The correct answer is (D).
Last edited by Rahul@gurome on Wed Sep 22, 2010 6:12 am, edited 1 time in total.
Rahul Lakhani
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
Top
User avatar
Community Manager
Posts: 1048
Joined: Mon Aug 17, 2009 3:26 am
Location: India
Thanked: 51 times
Followed by:27 members
GMAT Score:670

by arora007 » Wed Sep 22, 2010 2:44 am
OA is D, even i had selected B. see GMATFix is such a trap!! :)
https://www.skiponemeal.org/
https://twitter.com/skiponemeal
Few things are impossible to diligence & skill.Great works are performed not by strength,but by perseverance

pm me if you find junk/spam/abusive language, Lets keep our community clean!!
Top
Post new topic Post Reply
• Page 1 of 1