Find all School-related info fast with the new School-Specific MBA Forum

It is currently 25 Oct 2014, 20:24

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Quantitative review 2nd edition : DS 76. Is x between 0 and

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Director
Director
User avatar
Status: GMAT Learner
Joined: 14 Jul 2010
Posts: 650
Followers: 34

Kudos [?]: 254 [0], given: 32

Quantitative review 2nd edition : DS 76. Is x between 0 and [#permalink] New post 17 Jun 2011, 10:41
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

80% (01:18) correct 20% (01:12) wrong based on 10 sessions
Quantitative review 2nd edition : DS 76.
Is x between 0 and 1?
(1) x^2 is less than x.
(2) x^3 is positive

For (1) "OG explanation says that X^2 is positive so x positive."
But a negative x, x^2 is also positive. What is my wrong?
[Reveal] Spoiler: OA

_________________

I am student of everyone-baten
Collections:-
PSof OG solved by GC members: http://gmatclub.com/forum/collection-ps-with-solution-from-gmatclub-110005.html
DS of OG solved by GC members: http://gmatclub.com/forum/collection-ds-with-solution-from-gmatclub-110004.html
100 GMAT PREP Quantitative collection http://gmatclub.com/forum/gmat-prep-problem-collections-114358.html
Collections of work/rate problems with solutions http://gmatclub.com/forum/collections-of-work-rate-problem-with-solutions-118919.html
Mixture problems in a file with best solutions: http://gmatclub.com/forum/mixture-problems-with-best-and-easy-solutions-all-together-124644.html

1 KUDOS received
Math Forum Moderator
avatar
Joined: 20 Dec 2010
Posts: 2037
Followers: 128

Kudos [?]: 956 [1] , given: 376

Re: Is x between 0 and 1? [#permalink] New post 17 Jun 2011, 11:09
1
This post received
KUDOS
Baten80 wrote:
Quantitative review 2nd edition : DS 76.
Is x between 0 and 1?
(1) x^2 is less than x.
(2) x^3 is positive

For (1) "OG explanation says that X^2 is positive so x positive."
But a negative x, x^2 is also positive. What is my wrong?


If x^2 is less than x, then x must be +ve. Because, if x is -ve, x^2 will always be greater than x, not less.

Then comes the question whether x is between 0 and 1.
_________________

~fluke

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Manager
Manager
User avatar
Joined: 08 Sep 2010
Posts: 59
Followers: 0

Kudos [?]: 7 [0], given: 4

GMAT ToolKit User
Re: Is x between 0 and 1? [#permalink] New post 17 Jun 2011, 12:32
Baten80 wrote:
Quantitative review 2nd edition : DS 76.
Is x between 0 and 1?
(1) x^2 is less than x.
(2) x^3 is positive


Is x between 0 and 1? ---> is x a + fraction

(1) x^2 is less than x --> means x is a fraction because when fractions are squared, they are less then their original value

now if x was a (-) fraction, it would become greater than its original because its being squared. therefore x = (+) fraction

Suff.

(2) completely meaningless. just tells you that x is a positive. don't know if its a fraction or an integer

hence (a)
_________________

Don't forget to give me ****KUDOS****
;)

Manager
Manager
User avatar
Joined: 28 Feb 2011
Posts: 90
Followers: 0

Kudos [?]: 33 [0], given: 2

Re: Is x between 0 and 1? [#permalink] New post 17 Jun 2011, 13:20
A

x cannot be more than 1 because x^2>x then..same would be the case with x<0....but x^2<x holda true for all values between 0 and 1
_________________

Fight till you succeed like a gladiator..or doom your life which can be invincible

Director
Director
avatar
Joined: 01 Feb 2011
Posts: 768
Followers: 14

Kudos [?]: 58 [0], given: 42

CAT Tests
Re: Is x between 0 and 1? [#permalink] New post 17 Jun 2011, 16:27
is 0<x<1?

1. x^2<x

x^2-x<0
x(x-1)<0

solutions are x<0 & x>1 or x>0 & x<1

x<0 & x>1 is not possible. So only possible solution is x>0 & x<1. So sufficient

2. x^3>0

all we can say x>0

Not sufficient.

Answer is A.
Director
Director
avatar
Joined: 01 Feb 2011
Posts: 768
Followers: 14

Kudos [?]: 58 [0], given: 42

CAT Tests
Re: Is x between 0 and 1? [#permalink] New post 17 Jun 2011, 16:35
think this way

if x^2>0 , x can be positive or negative
but here we were told x^2<x. this will never be true for negative numbers as x^2 is always positive and will not
be less than a negative number.

=> x is positive. Now again x2<x will be true in the range of 0<x<1 .

Hence 0<x<1 . Hope its clear now.

Baten80 wrote:
Quantitative review 2nd edition : DS 76.
Is x between 0 and 1?
(1) x^2 is less than x.
(2) x^3 is positive

For (1) "OG explanation says that X^2 is positive so x positive."
But a negative x, x^2 is also positive. What is my wrong?
Re: Is x between 0 and 1?   [#permalink] 17 Jun 2011, 16:35
    Similar topics Author Replies Last post
Similar
Topics:
2 Experts publish their posts in the topic Official Guide for GMAT® Quantitative Review, 2nd Edition rajeshs 1 17 Jan 2014, 09:52
69 Experts publish their posts in the topic Quantitative Review, 2ND Edition Directory Bunuel 1 23 Dec 2013, 06:04
5 Experts publish their posts in the topic Quant Review 2nd Edition spreadsheet Big4Advisory 2 02 Apr 2013, 09:19
Official Guide Verbal review and Quant review (2nd edition) dreamchase 1 14 Nov 2011, 23:23
2 Experts publish their posts in the topic Is x^2 greater than x? 1) x^2 is greater than 1 2) x is jscott319 13 31 Oct 2010, 16:39
Display posts from previous: Sort by

Quantitative review 2nd edition : DS 76. Is x between 0 and

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.