Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 17 Aug 2009
Posts: 226

Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
03 Jan 2010, 09:49
3
This post received KUDOS
11
This post was BOOKMARKED
Question Stats:
55% (01:56) correct
45% (00:56) wrong based on 412 sessions
HideShow timer Statistics
Is xy + z = z, is xy > 0 ? (1) x ≠ 0 (2) y = 0
Official Answer and Stats are available only to registered users. Register/ Login.
Last edited by Bunuel on 23 Jan 2017, 04:04, edited 2 times in total.
Edited.



Verbal Forum Moderator
Joined: 02 Aug 2009
Posts: 4569

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
03 Jan 2010, 09:56
1
This post received KUDOS
Expert's post
2
This post was BOOKMARKED
A... from eq xy+z=z , we know xy is 0... for lxyl>0 xy ≠ 0... si) x ≠ 0 so y=0 and xy will be a ive or +ive no... suff sii) y=0... x can be 0 or any other no ...not suff
_________________
Absolute modulus :http://gmatclub.com/forum/absolutemodulusabetterunderstanding210849.html#p1622372 Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html



Intern
Joined: 30 Aug 2015
Posts: 31
Concentration: Marketing, Finance
WE: Brand Management (Manufacturing)

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
02 Sep 2015, 05:01
1
This post received KUDOS
zaarathelab wrote: Is xy + z = z, is xy > 0 ?
(1) x ≠ 0 (2) y = 0 KINDLY EXPLAIN STEP BY STEP
_________________
Please award kudos if you like my explanation. Thanks



Math Expert
Joined: 02 Sep 2009
Posts: 39683

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
02 Sep 2015, 05:48



Senior Manager
Joined: 20 Aug 2015
Posts: 396
Location: India

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
02 Sep 2015, 23:44
shakticnb wrote: zaarathelab wrote: Is xy + z = z, is xy > 0 ?
(1) x ≠ 0 (2) y = 0 KINDLY EXPLAIN STEP BY STEP Given: xy + z = z or xy = 0 Required: xy > 0. Statement 1: x ≠ 0 Under the given situation, xy = 0 only if y =0 Hence we have x > 0 The absolute value of any non zero number is always greater than 0 Hence we can definitely say that xy > 0 SUFFICIENTStatement 2: y = 0 This leaves us with x >0 But by xy = 0 we have either x = 0 or x ≠ 0 So, x = 0, or x >0 Not a definitive answer for xy INSUFFICIENT
_________________
Reach out to us at bondwithus@gmatify.com



Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 3460
GPA: 3.82

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
03 Sep 2015, 04:35
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 equations ensures a solution. Is xy + z = z, is xy > 0 ? (1) x ≠ 0 (2) y = 0 in the original condition we have xy+z=z, xy=0 and the question asks for xy>0? Since we have 2 variables and 1 equation, in order to match the number of variables and equations we need 1 more equation. Since there is 1 each in 1) and 2), D is likely the answer. In case of 1), y = 0 thus the answer is always yes. Therefore it is sufficient. In case of 2), x = 2 and y = 0 thus the answer is yes, but if x = 0 and y = 0 the answer is no. Therefore it is not sufficient. The answer is A
_________________
MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The oneandonly World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. Find a 10% off coupon code for GMAT Club members. “Receive 5 Math Questions & Solutions Daily” Unlimited Access to over 120 free video lessons  try it yourself See our Youtube demo



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15976

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
08 Oct 2016, 13:15
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



Intern
Joined: 06 Dec 2016
Posts: 3
Location: India
Concentration: General Management, Technology
GPA: 3.7
WE: Engineering (Military & Defense)

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
27 Dec 2016, 01:35
Easy, but the font is so small that the not equal sign was mistaken to be as =



Manager
Joined: 27 Aug 2016
Posts: 83
Location: India
GPA: 3
WE: Engineering (Energy and Utilities)

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
05 Jan 2017, 00:45
Bunuel wrote: shakticnb wrote: zaarathelab wrote: Is xy + z = z, is xy > 0 ?
(1) x ≠ 0 (2) y = 0 KINDLY EXPLAIN STEP BY STEP Is xy + z = z, is xy > 0 ?xy + z = z; Cancel z: xy = 0. This implies that either x or y (or both) is 0. (1) x ≠ 0. Since x is not 0, then y = 0. Thus the question becomes is x > 0. The absolute value of a nonzero number (x) is always positive. So, we have a definite YES answer to the question. Sufficient. (2) y = 0. The question becomes is x > 0. If x = 0, then the answer is NO but if x ≠ 0, then the answer is YES. Not sufficient. Answer: A. Hope it's clear. Hi Bunuel..well this analysis is clear and many thanx for it, but i went through a different route.. modulus of any number is always greater than zero...isn't it? so either satement alone could be the answer. In a recent exapmple this was the approach adopted the question was something like this (actual number may diifer)Is 7*mod(4xy)<14?? It was explained that modulus of 4xy would always be positive and when multiplied by a negative number it will always be negative...and THERE IS NO NEED TO ACTUALLY SOLVE...the inequality... Why can't we appply this approach here as well? Desparately need cl;arification



Math Expert
Joined: 02 Sep 2009
Posts: 39683

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
05 Jan 2017, 03:30
saurabhsavant wrote: Hi Bunuel..well this analysis is clear and many thanx for it, but i went through a different route.. modulus of any number is always greater than zero...isn't it? so either satement alone could be the answer.
In a recent exapmple this was the approach adopted
the question was something like this (actual number may diifer)Is 7*mod(4xy)<14?? It was explained that modulus of 4xy would always be positive and when multiplied by a negative number it will always be negative...and THERE IS NO NEED TO ACTUALLY SOLVE...the inequality...
Why can't we appply this approach here as well?
Desparately need cl;arification The absolute value of a number is always greater than or equal to 0. What I mean is that x = 0, when x = 0.
_________________
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? Extrahard Quant Tests with Brilliant Analytics



Intern
Joined: 18 Jan 2017
Posts: 38

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
23 Jan 2017, 03:57
1
This post received KUDOS
The question is typed as Is xy + z = z
Should it not be If xy + z = z
This created confusion for me.



Math Expert
Joined: 02 Sep 2009
Posts: 39683

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
23 Jan 2017, 04:05



Intern
Joined: 18 Jan 2017
Posts: 38

Re: Is xy + z = z, is xy > 0 ? [#permalink]
Show Tags
23 Jan 2017, 08:36
Thanks Bunuel! Now this makes much more sense.




Re: Is xy + z = z, is xy > 0 ?
[#permalink]
23 Jan 2017, 08:36







