GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 17 Feb 2019, 10:40

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 in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
  • Free GMAT Algebra Webinar

     February 17, 2019

     February 17, 2019

     07:00 AM PST

     09:00 AM PST

    Attend this Free Algebra Webinar and learn how to master Inequalities and Absolute Value problems on GMAT.
  • Valentine's day SALE is on! 25% off.

     February 18, 2019

     February 18, 2019

     10:00 PM PST

     11:00 PM PST

    We don’t care what your relationship status this year - we love you just the way you are. AND we want you to crush the GMAT!

If (x+y)/z = -2, is x positive?

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

Hide Tags

 
Retired Moderator
avatar
Joined: 29 Oct 2013
Posts: 257
Concentration: Finance
GPA: 3.7
WE: Corporate Finance (Retail Banking)
GMAT ToolKit User
If (x+y)/z = -2, is x positive?  [#permalink]

Show Tags

New post 14 Jan 2016, 10:48
1
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

74% (01:13) correct 26% (01:03) wrong based on 188 sessions

HideShow timer Statistics

If (x+y)/z = -2, is x positive?

(1) z is negative.
(2) y is positive.

_________________

Please contact me for super inexpensive quality private tutoring

My journey V46 and 750 -> http://gmatclub.com/forum/my-journey-to-46-on-verbal-750overall-171722.html#p1367876

CEO
CEO
avatar
S
Joined: 20 Mar 2014
Posts: 2629
Concentration: Finance, Strategy
Schools: Kellogg '18 (M)
GMAT 1: 750 Q49 V44
GPA: 3.7
WE: Engineering (Aerospace and Defense)
GMAT ToolKit User Premium Member Reviews Badge
Re: If (x+y)/z = -2, is x positive?  [#permalink]

Show Tags

New post 14 Jan 2016, 11:12
1
NoHalfMeasures wrote:
If (x+y)/z = -2, is x positive?

(1) z is negative.
(2) y is positive.


Is x>0?

Per statement 1, z<0 and with the given equation, (x+y)/z = -2 ---> z = -(x+y)/2 <0 ---> x+y >0 . Not sufficient (x=-5,y =6 NO but if x=5 , y =6 YES).

Per statement 2, y>0 and with the given equation, y=-2z-x >0 ---> -2z>x. Dont know the sign of z. Not sufficient.

Combining both statements, you get,

z<0 and y >0 ---> y=6, z=-1 will give you x = -4, and with y=6 and z=-4 will give you x=2. Thus both statements combined are not sufficient as well.

E is thus the correct answer.
CEO
CEO
User avatar
D
Joined: 11 Sep 2015
Posts: 3431
Location: Canada
Re: If (x+y)/z = -2, is x positive?  [#permalink]

Show Tags

New post 14 Jan 2016, 11:46
1
Nina1987 wrote:
If (x+y)/z = -2, is x positive?

(1) z is negative.
(2) y is positive.


Target question: Is x positive?

Given: (x + y)/z = -2
Since the question asks about the variable x, let's solve this equation for x.
(x + y)/z = -2
So, x + y = -2z
And, x = -2z - y

This allows us to REPHRASE the target question....
REPHRASED target question: Is -2z - y positive?

Aside: We have a free video with tips on rephrasing the target question: http://www.gmatprepnow.com/module/gmat-data-sufficiency?id=1100

Statement 1: z is negative
This statement doesn't FEEL sufficient, so I'll TEST some values.
There are several values of z that satisfy statement 1. Here are two:
Case a: z = -1 and y = 1. In this case -2z - y = -2(-1) - 1 = 1 = a POSITIVE NUMBER
Case b: z = -1 and y = 3. In this case -2z - y = -2(-1) - 3 = -1 = a NEGATIVE NUMBER
Since we cannot answer the REPHRASED target question with certainty, statement 1 is NOT SUFFICIENT

Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, you can read my article: http://www.gmatprepnow.com/articles/dat ... lug-values

Statement 2: y is positive
This statement doesn't FEEL sufficient either, so I'll TEST some values.
There are several values of y that satisfy statement 2. Here are two:
Case a: z = -1 and y = 1. In this case -2z - y = -2(-1) - 1 = 1 = a POSITIVE NUMBER
Case b: z = -1 and y = 3. In this case -2z - y = -2(-1) - 3 = -1 = a NEGATIVE NUMBER
Since we cannot answer the REPHRASED target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
There are several values of y and z that satisfy BOTH statements. Here are two:
Case a: z = -1 and y = 1. In this case -2z - y = -2(-1) - 1 = 1 = a POSITIVE NUMBER
Case b: z = -1 and y = 3. In this case -2z - y = -2(-1) - 3 = -1 = a NEGATIVE NUMBER
Since we cannot answer the REPHRASED target question with certainty, the combined statements are NOT SUFFICIENT

Answer = E
Cheers,
Brent
_________________

Test confidently with gmatprepnow.com
Image

Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 6949
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
Re: If (x+y)/z = -2, is x positive?  [#permalink]

Show Tags

New post 14 Jan 2016, 17:17
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

If (x+y)/z = -2, is x positive?

(1) z is negative.
(2) y is positive.

In the original condition, there are 3 variables(x,y,z) and 1 equation(x+y)/z = -2, which should match with the number of equations. So you need 2 equations. For 1) 1 equation, for 2) 1 equation, which is likely to make C the answer. When 1) & 2), it becomes z<0, y<0. In (x+y)/z = -2<0, x+y>0 when z<0. Even if y>0, it cannot be x>0, which is not sufficient. Therefore, the answer is E.


 For cases where we need 2 more equations, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $149 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Intern
Intern
avatar
B
Joined: 26 Dec 2018
Posts: 25
Concentration: Finance, Economics
Re: If (x+y)/z = -2, is x positive?  [#permalink]

Show Tags

New post 22 Jan 2019, 16:05
NoHalfMeasures wrote:
If (x+y)/z = -2, is x positive?

(1) z is negative.
(2) y is positive.


1. IF Z is negative, the sum of x+y would have to positive. However, we cannot definitively answer if x is positive because a variety of pairings could serve to ensure that x+y is positive, including negative numbers.
(insufficient)


2.If y is positive, either x,z or both could be negative. Insufficient.


Combined:We do not the extent to which y is positive, so x could be either positive or negative.

Please critique if you see fit!
GMATH Teacher
User avatar
G
Status: GMATH founder
Joined: 12 Oct 2010
Posts: 730
Re: If (x+y)/z = -2, is x positive?  [#permalink]

Show Tags

New post 29 Jan 2019, 05:26
NoHalfMeasures wrote:
If (x+y)/z = -2, is x positive?

(1) z is negative.
(2) y is positive.

\(x + y + 2z = 0\,\,\,,\,\,\,z \ne 0\,\,\,\)

\(x\,\,\mathop > \limits^? \,\,0\)


\(\left( {1 + 2} \right)\,\,y > 0\,\,,\,\,z < 0\,\,\,\,\,\left\{ \matrix{
\,{\rm{Take}}\,\,\left( {x,y,z} \right) = \left( {1,1, - 1} \right)\,\,\,\, \Rightarrow \,\,\,\left\langle {{\rm{YES}}} \right\rangle \,\, \hfill \cr
\,{\rm{Take}}\,\,\left( {x,y,z} \right) = \left( { - 1,3, - 1} \right)\,\,\,\, \Rightarrow \,\,\,\left\langle {{\rm{NO}}} \right\rangle \,\, \hfill \cr} \right.\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,\,\left( {\rm{E}} \right)\)


We follow the notations and rationale taught in the GMATH method.

Regards,
Fabio.
_________________

Fabio Skilnik :: GMATH method creator (Math for the GMAT)
Our high-level "quant" preparation starts here: https://gmath.net

GMAT Club Bot
Re: If (x+y)/z = -2, is x positive?   [#permalink] 29 Jan 2019, 05:26
Display posts from previous: Sort by

If (x+y)/z = -2, is x positive?

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


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.