what is the value of x y : Quant Question Archive [LOCKED]
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 24 Jan 2017, 06:08

### 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

# what is the value of x y

Author Message
Director
Joined: 19 Mar 2007
Posts: 524
Followers: 3

Kudos [?]: 32 [0], given: 0

what is the value of x y [#permalink]

### Show Tags

11 Jun 2007, 06:03
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

what is the value of x – y?

Last edited by nick_sun on 28 Jun 2008, 01:14, edited 1 time in total.
SVP
Joined: 01 May 2006
Posts: 1797
Followers: 9

Kudos [?]: 149 [0], given: 0

### Show Tags

11 Jun 2007, 07:25
(A) for me

x-y = ?

From 1
(x^2 – y^2) / (x + y) = 4
<=> (x-y) * (x+y) / (x+y) = 4
<=> x - y = 4

SUFF.

From 2
x + y = 7 >>> we can do nothing with it...

Picking numbers to be sure?
o If x=3 and y = 4, then x-y = -1
o If x=4 and y = 3, then x-y = 1

INSUFF.
Director
Joined: 19 Mar 2007
Posts: 524
Followers: 3

Kudos [?]: 32 [0], given: 0

### Show Tags

12 Jun 2007, 11:26
Thanks, Fig! The answer is A. Can't make myself factorize the quadratic equations
CEO
Joined: 17 May 2007
Posts: 2989
Followers: 60

Kudos [?]: 582 [0], given: 210

### Show Tags

12 Jun 2007, 23:49
Shouldn't the answer be C ?

Otherwise how would u know that x+y not equal to 0 ?

I remember a similar question in one of the challenges.
CEO
Joined: 17 May 2007
Posts: 2989
Followers: 60

Kudos [?]: 582 [0], given: 210

### Show Tags

12 Jun 2007, 23:50
I retract my earlier comment. x and y are positive hence A is indeed sufficient.
SVP
Joined: 01 May 2006
Posts: 1797
Followers: 9

Kudos [?]: 149 [0], given: 0

### Show Tags

12 Jun 2007, 23:56
bsd_lover wrote:
Shouldn't the answer be C ?

Otherwise how would u know that x+y not equal to 0 ?

I remember a similar question in one of the challenges.

x+y must be different from 0 because the equation exists and is stated ... It's true that in the real GMAT, it will be stated that x+y != 0 to avoid any confusion.

We just have to remove a solution to the equation that does x+y=0 if such a solution exists.

Here, we arrive to x-y = 4 and we should keep in mind that the intersection of the 2 lines x-y = 4 and x+y = 0 must be removed.... But for this problem, we do not care it
SVP
Joined: 01 May 2006
Posts: 1797
Followers: 9

Kudos [?]: 149 [0], given: 0

### Show Tags

12 Jun 2007, 23:59
bsd_lover wrote:
I retract my earlier comment. x and y are positive hence A is indeed sufficient.

Also yes
GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5062
Location: Singapore
Followers: 30

Kudos [?]: 358 [0], given: 0

### Show Tags

13 Jun 2007, 00:03
St1:
(x+y)(x-y)/(x+y) = 4
x-y = 4 --> sufficient.

St2:
x+y = 7, but there are many possible (x,y) solutions each giving different x-y results. --> insufficient.

ans A
Manager
Joined: 17 Oct 2006
Posts: 52
Followers: 0

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

### Show Tags

13 Jun 2007, 02:23
my vote is for A too.
Director
Joined: 30 Nov 2006
Posts: 591
Location: Kuwait
Followers: 14

Kudos [?]: 273 [0], given: 0

### Show Tags

13 Jun 2007, 06:48
(1) (x^2 – y^2) / (x + y) = 4
------------------------------------
(x^2 - y^2) = (x-y) (x+y)

Thus: (x^2 – y^2) / (x + y) = (x - y) = 4

statement 1 is sufficient

(2) x + y = 7
-----------------
Two variables one equation .. we can conclude nothing about x - y ..

statement 2 is insufficient

13 Jun 2007, 06:48
Display posts from previous: Sort by