Author 
Message 
TAGS:

Hide Tags

Retired Moderator
Joined: 29 Oct 2013
Posts: 248
Concentration: Finance
GPA: 3.7
WE: Corporate Finance (Retail Banking)

If (x + y)/z = 2, is x positive? (1) z is negative. (2) y is positive
[#permalink]
Show Tags
14 Jan 2016, 11:48
Question Stats:
69% (01:13) correct 31% (01:13) wrong based on 237 sessions
HideShow timer Statistics
If (x + y)/z = 2, is x positive? (1) z is negative. (2) y is positive.
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Please contact me for super inexpensive quality private tutoring
My journey V46 and 750 > http://gmatclub.com/forum/myjourneyto46onverbal750overall171722.html#p1367876



CEO
Joined: 20 Mar 2014
Posts: 2560
Concentration: Finance, Strategy
GPA: 3.7
WE: Engineering (Aerospace and Defense)

Re: If (x + y)/z = 2, is x positive? (1) z is negative. (2) y is positive
[#permalink]
Show Tags
14 Jan 2016, 12:12
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=2zx >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.



GMAT Club Legend
Joined: 12 Sep 2015
Posts: 4145
Location: Canada

Re: If (x + y)/z = 2, is x positive? (1) z is negative. (2) y is positive
[#permalink]
Show Tags
14 Jan 2016, 12:46
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  yThis 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/gmatdatasufficiency?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 ... lugvalues 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



Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 8257
GPA: 3.82

Re: If (x + y)/z = 2, is x positive? (1) z is negative. (2) y is positive
[#permalink]
Show Tags
14 Jan 2016, 18:17
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 spareThe oneandonly World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only $79 for 1 month Online Course""Free Resources30 day online access & Diagnostic Test""Unlimited Access to over 120 free video lessons  try it yourself"



Intern
Joined: 26 Dec 2018
Posts: 25
Concentration: Finance, Economics

Re: If (x + y)/z = 2, is x positive? (1) z is negative. (2) y is positive
[#permalink]
Show Tags
22 Jan 2019, 17:05
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
Status: GMATH founder
Joined: 12 Oct 2010
Posts: 935

Re: If (x + y)/z = 2, is x positive? (1) z is negative. (2) y is positive
[#permalink]
Show Tags
29 Jan 2019, 06:26
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 highlevel "quant" preparation starts here: https://gmath.net



Intern
Joined: 20 Jan 2019
Posts: 3

Re: If (x + y)/z = 2, is x positive? (1) z is negative. (2) y is positive
[#permalink]
Show Tags
03 Sep 2019, 10:55
We can solve this easily using logic. 1. As z is negative, (X+y) must be positive. But we cannot say whether x is positive or not. If y is positive and larger than x then x can be negative. But x can be positive also. So, insufficient. 2. If y is positive, x can be positive or negative. Insufficient. Taking both: as already said in statement 1, X can be negative if y is positive and larger than absolute value of x. So, the same result will come if x positive or negative. So Insufficient.
But if y is negative, then x must be positive. In that case the answer will be c.
So the answer is E
Posted from my mobile device



NonHuman User
Joined: 09 Sep 2013
Posts: 13740

Re: If (x + y)/z = 2, is x positive? (1) z is negative. (2) y is positive
[#permalink]
Show Tags
20 Oct 2019, 01:12
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.
_________________




Re: If (x + y)/z = 2, is x positive? (1) z is negative. (2) y is positive
[#permalink]
20 Oct 2019, 01:12






