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

Redeem

X is even

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Data Sufficiency |
User avatar
Legendary Member
Posts: 1893
Joined: Sun May 30, 2010 11:48 pm
Thanked: 215 times
Followed by:7 members

by kvcpk » Fri Jul 02, 2010 10:45 pm
taneja.niks wrote:another one guys

If x is an integer ,is x even?
1. x2-y2=0
2. x2+y2=18
x2-y2=0
let x=2, then y=2 or -2 [x is even]
x=3, then y=3 or -3 [x is odd]

INSUFFICIENT

x2+y2=18
x=3, y=3 or -3 [x is odd]
x=4, y=root(2) [x is even]

INSUFFICIENT

combining both, we get,
2x^2 = 18,
x^2=9
x = 3 or -3
answer is NO.

Pick C
Top

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 » Fri Jul 02, 2010 10:49 pm
Consider (1) alone first.
Given x2-y2 = 0. So (x+y)(x-y) = 0. Or x = -y or x = y.
From this we cannot judge whether x is even or not.
Examples are x= +2 and y = -2, x = +3 and y = 3.
In both case x2 - y2 is 0 but in one case x is even and in other case it is odd.
Or (1) alone is not sufficient.

Consider (2) alone first.
Let x = 2, y = sqrt(14). Here x2+y2 = 4 + 14 = 18. Here x is even.
Let x = 3, y = 3. Here x2+y2 = 9+9 = 18. Here x is odd.
Since we cannot say definitely whether x is even or odd, (2) alone is not sufficient.

Next combine both the statements together and check.
Add x2-y2=0 and x2+y2 = 18.
We have 2*x2 = 18.
Or x2 = 9.
Or x = +3 or -3.
Or we can say x is odd.
So x is not even.
The correct answer is hence (C).
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
Post new topic Post Reply
• Page 1 of 1