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

Redeem

Real numbers!!!

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |

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 Feb 19, 2013 5:31 am
rajatvmittal wrote:Is x a real number?

√x is not positive
x^2 is not positive
Statement 1: By definition, if x is a nonnegative real number then √x is always nonnegative. As √x is not positive, then we can only conclude that x is not a positive real number. But x can be either equal to zero or a negative real number or not real at all.

Not sufficient

Statement 2: As square of any real number is always nonnegative, x is either equal to zero or not real at all.

Not sufficient

1 & 2 Together: x is either equal to zero or not real at all.

Not sufficient

The correct answer is E.
Last edited by Anurag@Gurome on Tue Feb 19, 2013 8:52 am, edited 1 time in total.
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
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Tue Feb 19, 2013 5:35 am
Ignore this problem.
Imaginary numbers are beyond the scope of the GMAT.
An actual GMAT problem will never ask whether a value is real (versus imaginary).
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2623
Joined: Mon Jun 02, 2008 3:17 am
Location: Montreal
Thanked: 1090 times
Followed by:355 members
GMAT Score:780

by Ian Stewart » Tue Feb 19, 2013 8:44 am
Anurag@Gurome wrote:
Statement 2: As square of any real number is always positive, x is not a real number.
No, that's not the case. If x = 0, then x^2 is not positive.

But as Mitch says, every number on the GMAT is a real number. So if this were a GMAT question, you wouldn't need any Statements at all to answer this question - the answer must be 'yes' no matter what the Statements say.

Where are these questions from?
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com
Top

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 Feb 19, 2013 8:58 am
Ian Stewart wrote:... No, that's not the case. If x = 0, then x^2 is not positive.
Thanks for pointing it out, Ian.
I completely missed the x = 0 scenario.
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
Post new topic Post Reply
• Page 1 of 1