It is currently 19 Oct 2017, 22:35

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

M20-21

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41884

Kudos [?]: 128929 [0], given: 12183

M20-21 [#permalink]

Show Tags

New post 16 Sep 2014, 01:08
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

77% (00:57) correct 23% (00:40) wrong based on 31 sessions

HideShow timer Statistics

Kudos [?]: 128929 [0], given: 12183

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41884

Kudos [?]: 128929 [0], given: 12183

Re M20-21 [#permalink]

Show Tags

New post 16 Sep 2014, 01:08

Kudos [?]: 128929 [0], given: 12183

Intern
Intern
avatar
Joined: 20 Aug 2014
Posts: 5

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

Re: M20-21 [#permalink]

Show Tags

New post 04 Jan 2015, 15:17
the equation can be simplified as : Is square(x*y).square(y*z) > 0 . If we combine both the equation we find that neither x, y,z are zero. And after , even if (x*y) or (y*z) is positive/negative , the overall equation will be always positive as it the square of two non zeros . Am i doing something wrong .. Can you please clarify ?

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

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41884

Kudos [?]: 128929 [0], given: 12183

M20-21 [#permalink]

Show Tags

New post 05 Jan 2015, 05:50
jhasac wrote:
the equation can be simplified as : Is square(x*y).square(y*z) > 0 . If we combine both the equation we find that neither x, y,z are zero. And after , even if (x*y) or (y*z) is positive/negative , the overall equation will be always positive as it the square of two non zeros . Am i doing something wrong .. Can you please clarify ?


The point is that x^2*y^3*z^2 does NOT equal to (xy)^2*(yz)^2:

(xy)^2*(yz)^2 = x^2*y^4*z^2, not x^2*y^3*z^2.
_________________

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 [?]: 128929 [0], given: 12183

Intern
Intern
User avatar
Joined: 04 Mar 2016
Posts: 47

Kudos [?]: 11 [0], given: 2

Location: India
Re: M20-21 [#permalink]

Show Tags

New post 16 Dec 2016, 20:40
I have a query

Equation breaks down as xy.xy.yz.

From 1 we know xy is positive. We don't know yz so NS

From 2 we know yz is negatve. We don't know xy so NS

COMBINING WE KNOW XY IS POSITIVE AND YZ IS NEGATIVE. SO POSITIVE X POSITIVE X NEGATIVE = NEGATIVE. We have answer as NO.


SHUDNT IT BE C ??

Kudos [?]: 11 [0], given: 2

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41884

Kudos [?]: 128929 [0], given: 12183

Re: M20-21 [#permalink]

Show Tags

New post 17 Dec 2016, 03:56
Omkar.kamat wrote:
I have a query

Equation breaks down as xy.xy.yz.

From 1 we know xy is positive. We don't know yz so NS

From 2 we know yz is negatve. We don't know xy so NS

COMBINING WE KNOW XY IS POSITIVE AND YZ IS NEGATIVE. SO POSITIVE X POSITIVE X NEGATIVE = NEGATIVE. We have answer as NO.


SHUDNT IT BE C ??


\(xy*xy*yz=x^2y^3z\). You are missing one z. It's \(X^2Y^3Z^2\)
_________________

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 [?]: 128929 [0], given: 12183

Manager
Manager
avatar
G
Joined: 12 Jun 2016
Posts: 217

Kudos [?]: 34 [0], given: 124

Location: India
Concentration: Technology, Leadership
WE: Sales (Telecommunications)
GMAT ToolKit User CAT Tests
M20-21 [#permalink]

Show Tags

New post 12 Sep 2017, 22:31
Here's how I solved this.

STEM:

Is \(X^2Y^3Z^2 \gt 0\)

Since \(X^2\) and \(Z^2\) will ALWAYS be positive irrespective of their value, the stem can be Paraphrased as is - \(Y^3 \gt 0\). In plan english, What is the sign of Y?

S1:

\(XY \gt 0\)

Possible when both X&Y are positive or Both X&Y are negative. Meaning X can be either +ve or Negative. Insuff

S2:

\(YZ \lt 0\)

Same reasoning as S1. X could be +ve or -ve. Insuff

S1+S2:

Combining Both statements we get \(XY \gt YX\) => \(Y(X-Z) \gt 0\). This is still not enough to tell us tell us the exact sign of Y and Insuff

S1 Insuff. S2 Insuff. S1+S2 insuff. Final answer is E
_________________

My Best is yet to come!

Kudos [?]: 34 [0], given: 124

Director
Director
avatar
G
Joined: 26 Nov 2012
Posts: 593

Kudos [?]: 170 [0], given: 45

Premium Member CAT Tests
Re: M20-21 [#permalink]

Show Tags

New post 05 Oct 2017, 00:27
Buneul,

Kindly check on the below, we need to check whether \(x^2\) \(y^3\) \(z^2\) > 0 ?

Stat 1:
XY > 0 then we get two cases : case a) both positive and b) both negative

case a) When both +ve we get \(x^2\) \(y^3\) \(z^2\) as + + + > 0 (yes)
case b) when both -ve we get \(x^2\) \(y^3\) \(z^2\) as + - + < 0 (no)

Stat 2:
YZ < 0 then we get cases a) (y) +Ve and other -ve (z) and b) -ve (y)and other +ve(z)

case a) When y = +Ve and z = -ve we get \(x^2\) \(y^3\) \(z^2\) as + + + > 0 (yes)
case b) when y = -ve and z = +Ve we get \(x^2\) \(y^3\) \(z^2\) as + - + < 0 (no)

But in both statements when y is -ve then we get \(x^2\) \(y^3\) \(z^2\) < 0... right ? why this is not considered in official solution..plz let me know.

Kudos [?]: 170 [0], given: 45

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41884

Kudos [?]: 128929 [0], given: 12183

Re: M20-21 [#permalink]

Show Tags

New post 05 Oct 2017, 00:45
msk0657 wrote:
Buneul,

Kindly check on the below, we need to check whether \(x^2\) \(y^3\) \(z^2\) > 0 ?

Stat 1:
XY > 0 then we get two cases : case a) both positive and b) both negative

case a) When both +ve we get \(x^2\) \(y^3\) \(z^2\) as + + + > 0 (yes)
case b) when both -ve we get \(x^2\) \(y^3\) \(z^2\) as + - + < 0 (no)

Stat 2:
YZ < 0 then we get cases a) (y) +Ve and other -ve (z) and b) -ve (y)and other +ve(z)

case a) When y = +Ve and z = -ve we get \(x^2\) \(y^3\) \(z^2\) as + + + > 0 (yes)
case b) when y = -ve and z = +Ve we get \(x^2\) \(y^3\) \(z^2\) as + - + < 0 (no)

But in both statements when y is -ve then we get \(x^2\) \(y^3\) \(z^2\) < 0... right ? why this is not considered in official solution..plz let me know.


What are you implying?

For (1)+(2) x and y have the same sign and y and z have the opposite sign:

x > 0, y > 0 and z < 0, then x^2*y^3*z^2 = positive*positive*positive > 0;
x < 0, y < 0 and z > 0, then x^2*y^3*z^2 = positive*negative*positive > 0.
_________________

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 [?]: 128929 [0], given: 12183

Re: M20-21   [#permalink] 05 Oct 2017, 00:45
Display posts from previous: Sort by

M20-21

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

Moderators: Bunuel, Vyshak



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®.