It is currently 28 Jun 2017, 04:05

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Is x>y?

Author Message
TAGS:

### Hide Tags

Current Student
Joined: 19 Dec 2011
Posts: 12
Concentration: Healthcare, Operations
Schools: Olin '17 (M)
GPA: 3.24
WE: Supply Chain Management (Military & Defense)

### Show Tags

20 Aug 2013, 22:03
1
This post was
BOOKMARKED
00:00

Difficulty:

45% (medium)

Question Stats:

62% (02:02) correct 38% (01:04) wrong based on 210 sessions

### HideShow timer Statistics

Is x>y?

(1) x+y>0
(2) x^2-y^2>0

[Reveal] Spoiler:
For 1) x+y>0
x> -y Insufficient

For 2) x^2-y^2>0
x^2>y^2
--> x<-y OR x>y

1) and 2)
x> -y
and x<-y OR x>y

So the answer should be E.
However, the answer key says C. What concept am I missing?

Thanks.

[Reveal] Spoiler: OA

Last edited by Bunuel on 21 Aug 2013, 01:20, edited 2 times in total.
Edited the question.
Math Expert
Joined: 02 Sep 2009
Posts: 39744

### Show Tags

21 Aug 2013, 01:27
3
KUDOS
Expert's post
1
This post was
BOOKMARKED
Is x>y?

Is x>y? --> is x-y>0?

(1) x+y>0. The sum of two numbers is greater than 0, from this we cannot say which one is greater. Consider (x, y)=(1, 2) and (x, y)=(2, 1). Not sufficient.

(2) x^2-y^2>0 --> x^2>y^2 --> |x|>|y|. This implies that x is further from 0, then y is. Not sufficient. Consider: (x, y)=(-2, 1) and (x, y)=(2, 1).

(1)+(2) From (2) we have that (x-y)(x+y)>0 and from (1) we have that x+y>0, thus x-y>0. Sufficient.

Hope it's clear.
_________________
Intern
Joined: 21 Jul 2013
Posts: 1

### Show Tags

21 Aug 2013, 17:05
Bunuel:

Your answer totally makes sense - I'm curious, what led you to immediately jump to X>Y --> X-Y>0? To be honest, if I saw the question in the latter form, my first instinct would be to assume that the real question to be is X>Y?. Appreciate the help!
Math Expert
Joined: 02 Sep 2009
Posts: 39744

### Show Tags

22 Aug 2013, 02:41
2
KUDOS
Expert's post
mid14 wrote:
Bunuel:

Your answer totally makes sense - I'm curious, what led you to immediately jump to X>Y --> X-Y>0? To be honest, if I saw the question in the latter form, my first instinct would be to assume that the real question to be is X>Y?. Appreciate the help!

Hard to say. When I see x>y, I automatically see x-y>0. Guess it comes with practice.
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16018

### Show Tags

10 Nov 2015, 01:50
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.
_________________
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 3472
GPA: 3.82

### Show Tags

15 Nov 2015, 01:47
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.

Is x>y?

(1) x+y>0
(2) x^2-y^2>0

There are 2 variables (x,y) and 2 equations are given from the 2 conditions, making it likely that (C) will be our answer.
Looking at them together,
x+y>0 and (x-y)(x+y)>0, x+y>0, so x-y>0. This answers the question 'yes' and it is therefore sufficient; the answer is (C).

For cases where we need 2 more equation, 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.
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

Re: Is x>y?   [#permalink] 15 Nov 2015, 01:47
Similar topics Replies Last post
Similar
Topics:
8 Is x^2>y^2? 3 21 May 2017, 23:05
7 Is x^2>y^2? 12 23 Feb 2017, 04:47
8 If x and y are integers, is (x−1)>y? 10 09 Oct 2016, 17:50
232 Is x > y ? (1) x^(1/2)>y (2) x^3>y 41 18 Mar 2017, 20:32
29 If y>=0, What is the value of x? (1) |x-3|>=y (2) |x-3|<=-y 21 18 Oct 2016, 03:32
Display posts from previous: Sort by