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

It is currently 27 Jul 2014, 22:17

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

Is Z less than 0?

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 06 Jul 2011
Posts: 214
Location: Accra, Ghana
Followers: 1

Kudos [?]: 21 [0], given: 39

GMAT Tests User
Is Z less than 0? [#permalink] New post 20 Mar 2012, 00:03
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

89% (01:27) correct 11% (00:54) wrong based on 46 sessions
Is z less than 0?

(1) xy>0 and yz<0
(2) x>0
[Reveal] Spoiler: OA
Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 18790
Followers: 3259

Kudos [?]: 22561 [1] , given: 2630

Re: Is Z less than 0? [#permalink] New post 20 Mar 2012, 00:21
1
This post received
KUDOS
Expert's post
Is z less than 0?

(1) xy>0 and yz<0 --> first inequality is useless for us since it has no z. From yz<0 we can say that y and z have opposite sings, but we don't know the sign of y to deduce something about z. Not sufficient.

(2) x>0. Not sufficient.

(1)+(2) From xy>0 we can say that x and y have the same sign, and since from (2) x>0 then y>0 too. Now, from yz<0 we have that y and z have opposite sings and as y>0 then z<0. Sufficient.

Answer: C.

Hope it's clear.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Senior Manager
Senior Manager
User avatar
Status: May The Force Be With Me (D-DAY 15 May 2012)
Joined: 06 Jan 2012
Posts: 292
Location: India
Concentration: General Management, Entrepreneurship
Followers: 1

Kudos [?]: 68 [0], given: 16

Reviews Badge
Re: Is Z less than 0? [#permalink] New post 20 Mar 2012, 00:28
Hi,

I hope this helps

We have to prove that Is z < 0?
Statement 1. xy>0 and yz<0
=> x & y are negative / x & y are positive
=> z is postive / z is negative
Hence Insufficient

2. x>0
Insufficient since nothing said about y or z

Combine
X is positive
= >X is positive Y is positive Thus Z is negative

Hence sufficient
_________________

Giving +1 kudos is a better way of saying 'Thank You'.

Manager
Manager
avatar
Joined: 12 Dec 2012
Posts: 230
Concentration: Leadership, Marketing
GMAT 1: 540 Q36 V28
GMAT 2: 550 Q39 V27
GMAT 3: 620 Q42 V33
GPA: 2.82
WE: Human Resources (Health Care)
Followers: 2

Kudos [?]: 41 [0], given: 181

Re: Is Z less than 0? [#permalink] New post 14 Mar 2013, 18:28
Bunuel wrote:
Is z less than 0?

(1) xy>0 and yz<0 --> first inequality is useless for us since it has no z. From yz<0 we can say that y and z have opposite sings, but we don't know the sign of y to deduce something about z. Not sufficient.

(2) x>0. Not sufficient.

(1)+(2) From xy>0 we can say that x and y have the same sign, and since from (2) x>0 then y>0 too. Now, from yz<0 we have that y and z have opposite sings and as y>0 then z<0. Sufficient.

Answer: C.

Hope it's clear.


for the first statement I concluded that x and y have the same signs and since y times z is negative so z is the opposite sign . I made a chart trying +/- signs for each until I got A ... still cannot quite understand why C ?
_________________

My RC Recipe
http://gmatclub.com/forum/the-rc-recipe-149577.html

My Problem Takeaway Template
http://gmatclub.com/forum/the-simplest-problem-takeaway-template-150646.html

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 18790
Followers: 3259

Kudos [?]: 22561 [0], given: 2630

Re: Is Z less than 0? [#permalink] New post 15 Mar 2013, 00:14
Expert's post
TheNona wrote:
Bunuel wrote:
Is z less than 0?

(1) xy>0 and yz<0 --> first inequality is useless for us since it has no z. From yz<0 we can say that y and z have opposite sings, but we don't know the sign of y to deduce something about z. Not sufficient.

(2) x>0. Not sufficient.

(1)+(2) From xy>0 we can say that x and y have the same sign, and since from (2) x>0 then y>0 too. Now, from yz<0 we have that y and z have opposite sings and as y>0 then z<0. Sufficient.

Answer: C.

Hope it's clear.


for the first statement I concluded that x and y have the same signs and since y times z is negative so z is the opposite sign . I made a chart trying +/- signs for each until I got A ... still cannot quite understand why C ?


Yes, xy > 0, means that x and y are either both positive or both negative. But this does not help us much.

yz < 0 means that y and z have the opposite signs. So, if y is negative then z is positive and if y is positive then z negative. Hence from the first statement z could be positive as well as negative.

Hope it's clear.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Re: Is Z less than 0?   [#permalink] 15 Mar 2013, 00:14
    Similar topics Author Replies Last post
Similar
Topics:
2 Experts publish their posts in the topic Is z less than 0? Bunuel 5 18 Feb 2014, 02:44
4 Experts publish their posts in the topic If x is a positive number less than 10, is z less than the metallicafan 11 25 Apr 2012, 10:22
Experts publish their posts in the topic Is z less than 0? metallicafan 5 14 Dec 2011, 08:57
Experts publish their posts in the topic If x > y > z, is xz positive? (1) xy is less than 0 tarek99 1 30 Nov 2007, 09:46
If ZY<XY<0 , is |X-Z|+|X|=|Z| 1. Z is less than X 2. Y trahul4 3 09 Aug 2007, 18:39
Display posts from previous: Sort by

Is Z less than 0?

  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®.