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

It is currently 02 Jul 2016, 01:34
GMAT Club Tests

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

If x is not equal to zero is xy > 0 ?

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

Hide Tags

Intern
Intern
avatar
Joined: 12 Jul 2012
Posts: 31
Followers: 0

Kudos [?]: 72 [0], given: 1

If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 24 Sep 2012, 23:06
2
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

61% (01:54) correct 39% (00:39) wrong based on 153 sessions

HideShow timer Statistics

If x is not equal to zero is xy > 0 ?

(1) x >0

(2) 1/x < y
[Reveal] Spoiler: OA

Last edited by Bunuel on 25 Sep 2012, 01:22, edited 1 time in total.
Edited the question.
Expert Post
1 KUDOS received
GMAT Tutor
avatar
Joined: 24 Jun 2008
Posts: 1181
Followers: 379

Kudos [?]: 1286 [1] , given: 4

Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 25 Sep 2012, 00:04
1
This post received
KUDOS
Expert's post
harikris wrote:

If x is not equal to zero is xy > 0 ?

1) x >0

2) 1/x < y


xy will be positive if x and y have the same sign. Statement 1 gives no information about y, and from Statement 2, it is possible that x and y are both positive or both negative, or that x is negative and y is positive.

Using both statements, we know x is positive, so 1/x is positive. From Statement 2, if y > 1/x, then y is greater than something positive, so y is also positive, and xy is positive, so the answer is C.
_________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

Expert Post
2 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 33601
Followers: 5957

Kudos [?]: 74045 [2] , given: 9908

Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 25 Sep 2012, 01:28
2
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
If x is not equal to zero is xy > 0 ?

xy will be positive if x and y have the same sign, when both are negative or both are positive.

(1) x > 0. No info about \(y\). Not sufficient.

(2) 1/x < y. If \(x=-1\) and \(y=1\) then the answer is NO but if \(x=2\) and \(y=1\) then the answer is YES. Not sufficient.

(1)+(2) Since from (1) \(x>0\), then \(\frac{1}{x}>0\), hence from (2) we have that \(0<\frac{1}{x}<y\) --> \(y>0\). Thus both \(x\) and \(y\) are positive. Sufficient.

Answer: C.
_________________

New to the Math Forum?
Please read this: 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

Intern
Intern
avatar
Joined: 12 Sep 2012
Posts: 2
Followers: 0

Kudos [?]: 0 [0], given: 1

Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 27 Sep 2012, 12:53
Sorry but I don't understand why the answer can not be B.

B) 1/x < y This can be transformed in xy > 1. So if xy>1 it should be also true xy > 0.

Please could you tell me where I am wrong?

Thank you
Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 33601
Followers: 5957

Kudos [?]: 74045 [1] , given: 9908

Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 27 Sep 2012, 13:01
1
This post received
KUDOS
Expert's post
Marcyfal wrote:
Sorry but I don't understand why the answer can not be B.

B) 1/x < y This can be transformed in xy > 1. So if xy>1 it should be also true xy > 0.

Please could you tell me where I am wrong?

Thank you


Never multiply an inequality by variable (or expression with variable) unless you know the sign of variable (or expression with variable). Because if \(x>0\) you should write \(xy>1\) BUT if \(x<0\), you should write \(xy<1\) (flip the sign when multiplying by negative expression).

Hope it helps.
_________________

New to the Math Forum?
Please read this: 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

Intern
Intern
avatar
Joined: 12 Sep 2012
Posts: 2
Followers: 0

Kudos [?]: 0 [0], given: 1

Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 27 Sep 2012, 13:31
All right, Thank you very much. By the way I follow all your answers. You are great!
Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 33601
Followers: 5957

Kudos [?]: 74045 [0], given: 9908

Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 06 Sep 2013, 00:28
Expert's post
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 10262
Followers: 483

Kudos [?]: 124 [0], given: 0

Premium Member
Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 19 Jan 2016, 01:51
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Expert Post
1 KUDOS received
VP
VP
User avatar
Joined: 08 Jul 2010
Posts: 1194
Location: India
GMAT: INSIGHT
WE: Education (Education)
Followers: 43

Kudos [?]: 1006 [1] , given: 40

Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 19 Jan 2016, 06:36
1
This post received
KUDOS
Expert's post
harikris wrote:
If x is not equal to zero is xy > 0 ?

(1) x >0

(2) 1/x < y


Question : Is xy > 0?

Statement 1: x>0
i.e. x is positive but we have no information about y being positive or Negtive, Hence
NOT SUFFICIENT

Statement 2: 1/x<y
This relation will be true for x=-1 and y=2 i.e. xy<0
or x= 1 and y = 2 i.e. xy>0
NOT SUFFICIENT

Combining the two statements
x is positive and y>1/x i.e. y too is positive
hence, xy>0
SUFFICIENT

Answer: Option C
_________________

Prosper!!!

GMATinsight

Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com
Call us : +91-9999687183 / 9891333772
http://www.GMATinsight.com/testimonials.html


Contact for One-on-One LIVE ONLINE (SKYPE Based) or CLASSROOM Quant/Verbal FREE Demo Class



READ: http://gmatclub.com/forum/620-to-760-getting-reborn-161230.html
Classroom Centre Address:
GMATinsight
107, 1st Floor, Krishna Mall, Sector-12 (Main market), Dwarka, New Delhi-110075

______________________________________________________
Please press the Image if you appreciate this post !!

Intern
Intern
avatar
Joined: 05 Jul 2013
Posts: 4
Followers: 0

Kudos [?]: 0 [0], given: 3

Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 20 Jan 2016, 10:37
hi bunuel,

Cant we write the option B as y>1/x= (x-y)/x>0 and if you put both the statements together and try few values as mentioned below it is satisfying for neg/pos value of Y.

X=10 Y=8 and X=10 and Y=-8 in both cases above equation holds.

Kindly explain!! Thanks
Expert Post
1 KUDOS received
VP
VP
User avatar
Joined: 08 Jul 2010
Posts: 1194
Location: India
GMAT: INSIGHT
WE: Education (Education)
Followers: 43

Kudos [?]: 1006 [1] , given: 40

Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 20 Jan 2016, 10:44
1
This post received
KUDOS
Expert's post
rocky1988 wrote:
hi bunuel,

Cant we write the option B as y>1/x= (x-y)/x>0 and if you put both the statements together and try few values as mentioned below it is satisfying for neg/pos value of Y.

X=10 Y=8 and X=10 and Y=-8in both cases above equation holds.

Kindly explain!! Thanks


y is NOT greater than 1/x as per highlighted set of values so they can't be taken as they violate the information os Second statement.

I hope this helps
_________________

Prosper!!!

GMATinsight

Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com
Call us : +91-9999687183 / 9891333772
http://www.GMATinsight.com/testimonials.html


Contact for One-on-One LIVE ONLINE (SKYPE Based) or CLASSROOM Quant/Verbal FREE Demo Class



READ: http://gmatclub.com/forum/620-to-760-getting-reborn-161230.html
Classroom Centre Address:
GMATinsight
107, 1st Floor, Krishna Mall, Sector-12 (Main market), Dwarka, New Delhi-110075

______________________________________________________
Please press the Image if you appreciate this post !!

Expert Post
Math Forum Moderator
avatar
Joined: 20 Mar 2014
Posts: 2614
Concentration: Finance, Strategy
Schools: Kellogg '18 (M)
GMAT 1: 750 Q49 V44
GPA: 3.7
WE: Engineering (Aerospace and Defense)
Followers: 101

Kudos [?]: 1131 [0], given: 781

Re: If x is not equal to zero is xy > 0 ? [#permalink]

Show Tags

New post 20 Jan 2016, 11:02
Expert's post
rocky1988 wrote:
hi bunuel,

Cant we write the option B as y>1/x= (x-y)/x>0and if you put both the statements together and try few values as mentioned below it is satisfying for neg/pos value of Y.

X=10 Y=8 and X=10 and Y=-8 in both cases above equation holds.

Kindly explain!! Thanks


You can not perform the calculations you have mentioned above.

y>1/x \(\neq\) (x-y)/x>0

You can although, rewrite statement 2 as y-1/x > 0 --->(xy-1)/x>0 and as x>0 ---> for this fraction to be >0 --> xy-1>0 ---> xy>1 . Again, 2 cases possible, x>0 and y>0 and x<0 and y<0. Thus this statement is NOT sufficient.
_________________

Thursday with Ron updated list as of July 1st, 2015: http://gmatclub.com/forum/consolidated-thursday-with-ron-list-for-all-the-sections-201006.html#p1544515
Rules for Posting in Quant Forums: http://gmatclub.com/forum/rules-for-posting-please-read-this-before-posting-133935.html
Writing Mathematical Formulae in your posts: http://gmatclub.com/forum/rules-for-posting-please-read-this-before-posting-133935.html#p1096628
GMATCLUB Math Book: http://gmatclub.com/forum/gmat-math-book-in-downloadable-pdf-format-130609.html
Everything Related to Inequalities: http://gmatclub.com/forum/inequalities-made-easy-206653.html#p1582891
Inequalities tips: http://gmatclub.com/forum/inequalities-tips-and-hints-175001.html
Debrief, 650 to 750: http://gmatclub.com/forum/650-to-750-a-10-month-journey-to-the-score-203190.html

Re: If x is not equal to zero is xy > 0 ?   [#permalink] 20 Jan 2016, 11:02
    Similar topics Author Replies Last post
Similar
Topics:
7 Experts publish their posts in the topic Is x^y > 0 ? Bunuel 4 23 Sep 2015, 03:36
4 Experts publish their posts in the topic If x ≠ 0, is xy > 0? Bunuel 8 19 Jun 2015, 01:58
6 Experts publish their posts in the topic If x and y cannot be equal to zero, is x/y > y/x ? Bunuel 7 27 Nov 2014, 07:47
9 Experts publish their posts in the topic If xy#0, is x^y > 0 ? Bunuel 9 20 Jul 2014, 11:23
9 Experts publish their posts in the topic If x > 0, is x/y > x ? amitgovin 14 08 Oct 2009, 13:27
Display posts from previous: Sort by

If x is not equal to zero is xy > 0 ?

  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 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®.