It is currently 12 Dec 2017, 19:37

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Is |x| < 1 ? 1. x^4 - 1 > 0 2.

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Manager
Manager
avatar
Joined: 20 Apr 2010
Posts: 151

Kudos [?]: 19 [0], given: 16

Location: I N D I A
Is |x| < 1 ? 1. x^4 - 1 > 0 2. [#permalink]

Show Tags

New post 27 Jul 2010, 06:27
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

50% (01:25) correct 50% (01:29) wrong based on 10 sessions

HideShow timer Statistics

Is |x| < 1 ?
1. \(x^4\) - 1 > 0
2. \((1/(1-|x|))\) > 0




One more basic doubt i ve regarding DS ?

Say If statement 1 . gives values of y as 0 , 1 , 2 , 3
Say If statement 2 . gives values of y as 1 , 2 , 3

Then while checking for C do we have to include 0 OR we just have to take common values i.e. 1,2,3 and not 0.. i hope i am able to make my Q clear.. I am missing somewhere..

Thanks

Kudos [?]: 19 [0], given: 16

Manager
Manager
avatar
Joined: 09 Jan 2010
Posts: 123

Kudos [?]: 42 [0], given: 12

Re: Dont have the official Ans for this.. [#permalink]

Show Tags

New post 27 Jul 2010, 07:20
as per cond 1

x^4 -1 > 0
-> X^4 > 1

i.e x can be -2, -3 .... ,2 , 3 , 4.....
mod x is always greater than 1
sufficient

as per cond 2

1/ (1-MOD X ) >0
i.e 1-mod x> 0
i.e 1> mod x

hence sufficient

answer D

Kudos [?]: 42 [0], given: 12

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 42575

Kudos [?]: 135405 [0], given: 12692

Re: Dont have the official Ans for this.. [#permalink]

Show Tags

New post 27 Jul 2010, 07:49
sag wrote:
Is |x| < 1 ?
1. \(x^4\) - 1 > 0
2. \((1/(1-|x|))\) > 0

Thanks

Not a good question.

Is \(|x| < 1\)? --> is \(-1<x<1\)?

(1) \(x^4-1>0\) --> \(x^4>1\) --> \(x<-1\) or \(x>1\). So \(x\) is not in the range (-1,1). Sufficient.

(2) \(\frac{1}{1-|x|}>0\) --> nominator is positive thus denominator must also be positive for fraction to be positive --> \(1-|x|>0\) --> \(|x|<1\). Sufficient.

Answer: D.

But: From (1) we have that \(x\) is NOT in the range (-1,1) and from (2) that \(x\) is in the range (-1,1). Two statements contradict each other.

This will never occur on GMAT as: on the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other.

sag wrote:
One more basic doubt i ve regarding DS ?

Say If statement 1 . gives values of y as 0 , 1 , 2 , 3
Say If statement 2 . gives values of y as 1 , 2 , 3

Then while checking for C do we have to include 0 OR we just have to take common values i.e. 1,2,3 and not 0.. i hope i am able to make my Q clear.. I am missing somewhere..

Thanks

Consider the following question (I just made it up):

If \(y\) is an integer, is \(|y+1|<3\)?

\(|y+1|<3\) means is \(-4<y<2\) (-3, -2, -1, 0, 1)?

(1) \(-3<y^3<10\) --> \(y\) can be: -1, 0, 1, or 2. Not sufficient.

(2) \((y^2+4y)(y-1)=0\) --> \(y\) can be: -4, 0, or 1. Not sufficient.

(1)+(2) Intersection of the values from (1) and (2) are \(y=0\) and \(y=1\), both these values satisfy inequality \(|y+1|<3\). Sufficient.

Answer: C.

So if statement (1) gives one set of values for x and statement (2) gives another set of values for x, then when considering statements together we should take only the values which satisfy both statements.

Hope it helps.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 135405 [0], given: 12692

Manager
Manager
avatar
Joined: 20 Apr 2010
Posts: 151

Kudos [?]: 19 [0], given: 16

Location: I N D I A
Re: Dont have the official Ans for this.. [#permalink]

Show Tags

New post 27 Jul 2010, 23:24
Bunuel wrote:
sag wrote:
Is |x| < 1 ?
1. \(x^4\) - 1 > 0
2. \((1/(1-|x|))\) > 0

Thanks

Not a good question.

Is \(|x| < 1\)? --> is \(-1<x<1\)?

(1) \(x^4-1>0\) --> \(x^4>1\) --> \(x<-1\) or \(x>1\). So \(x\) is not in the range (-1,1). Sufficient.

(2) \(\frac{1}{1-|x|}>0\) --> nominator is positive thus denominator must also be positive for fraction to be positive --> \(1-|x|>0\) --> \(|x|<1\). Sufficient.

Answer: D.

But: From (1) we have that \(x\) is NOT in the range (-1,1) and from (2) that \(x\) is in the range (-1,1). Two statements contradict each other.

This will never occur on GMAT as: on the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other.

sag wrote:
One more basic doubt i ve regarding DS ?

Say If statement 1 . gives values of y as 0 , 1 , 2 , 3
Say If statement 2 . gives values of y as 1 , 2 , 3

Then while checking for C do we have to include 0 OR we just have to take common values i.e. 1,2,3 and not 0.. i hope i am able to make my Q clear.. I am missing somewhere..

Thanks

Consider the following question (I just made it up):

If \(y\) is an integer, is \(|y+1|<3\)?

\(|y+1|<3\) means is \(-4<y<2\) (-3, -2, -1, 0, 1)?

(1) \(-3<y^3<10\) --> \(y\) can be: -1, 0, 1, or 2. Not sufficient.

(2) \((y^2+4y)(y-1)=0\) --> \(y\) can be: -4, 0, or 1. Not sufficient.

(1)+(2) Intersection of the values from (1) and (2) are \(y=0\) and \(y=1\), both these values satisfy inequality \(|y+1|<3\). Sufficient.

Answer: C.

So if statement (1) gives one set of values for x and statement (2) gives another set of values for x, then when considering statements together we should take only the values which satisfy both statements.

Hope it helps.


Thanks Bunuel once again for both the explanations.. u rock...

Kudos [?]: 19 [0], given: 16

Re: Dont have the official Ans for this..   [#permalink] 27 Jul 2010, 23:24
Display posts from previous: Sort by

Is |x| < 1 ? 1. x^4 - 1 > 0 2.

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


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

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

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®.