Find all School-related info fast with the new School-Specific MBA Forum

It is currently 25 Oct 2014, 21:16

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

In which quadrant of the coordinate plane does the point

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
avatar
Joined: 20 Jun 2009
Posts: 8
Followers: 0

Kudos [?]: 1 [0], given: 0

In which quadrant of the coordinate plane does the point [#permalink] New post 14 Jul 2009, 06:22
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

69% (01:45) correct 31% (01:28) wrong based on 38 sessions
In which quadrant of the coordinate plane does the point (x, y) lie?

(1) |xy| + x|y| + |x|y + xy > 0
(2) -x < -y < |y|

OPEN DISCUSSION OF THIS QUESTION IS HERE: in-which-quadrant-of-the-coordinate-plane-does-the-point-86767.html
[Reveal] Spoiler: OA

Last edited by Bunuel on 18 Jun 2012, 00:14, edited 1 time in total.
TOPIC LOCKED
Kaplan GMAT Prep Discount CodesKnewton GMAT Discount CodesManhattan GMAT Discount Codes
1 KUDOS received
Current Student
User avatar
Status: What's your raashee?
Joined: 12 Jun 2009
Posts: 1847
Location: United States (NC)
Concentration: Strategy, Finance
Schools: UNC (Kenan-Flagler) - Class of 2013
GMAT 1: 720 Q49 V39
WE: Programming (Computer Software)
Followers: 22

Kudos [?]: 202 [1] , given: 52

Reviews Badge
Re: DS question - Help [#permalink] New post 14 Jul 2009, 07:25
1
This post received
KUDOS
Wengen wrote:
Hi Guys,

Can you please help with the following DS question

In which quadrant of the coordinate plane does the point (x, y) lie?

(1) |xy| + x|y| + |x|y + xy > 0
(2) -x < -y < |y|


I chose ans B but the right answer seems to be D - Each stmt alone is sufficient.


since you understood B works i will help on A(1).
I just used basic POE assuming XY,X(-Y),(-X)Y, (-X)(-Y) representing the 4 quadrants.
XY: XY +XY+XY+XY >0 TRUE
X(-Y): XY+XY-XY-XY >0 FALSE
(-X)Y: XY-XY+XY-XY>0 FALSE
(-X)(-Y): XY-XY-XY+XY>0 FALSE

hope it helps kudos
_________________

If you like my answers please +1 kudos!

Manager
Manager
avatar
Joined: 07 Apr 2009
Posts: 145
Followers: 1

Kudos [?]: 9 [0], given: 3

Re: DS question - Help [#permalink] New post 14 Jul 2009, 10:14
Trying to learn !

When ever I see a |mod| I do one iteration by keeping all positives and next iteration by removing the |mod|

so when keep the |mod| in the first option I get..

4xy > 0 then xy >0 , which shows either its in Quadrant 1 or Q4

then coming to removing mod symbol, i get
-xy-xy-xy+xy = -2xy >0 which is xy < 0 which contradicts the result that I got above, so I stopped there... what is wrong with my approach ?

I solved the B in the same lines...

-x < -y <|y|
1) -x <-y --> x > y
2) -y < |y|
so -y < y or -y < -y
y > 0 or 0 > 0

second 0>0 is wrong so concluded y > 0 , when y >0 and x > y (x,y) lies in Q1. thats how I concluded B

Guys I am in serious trouble I just dont understnad how to proceed with modulus, I get freezed looking at them :)
Manager
Manager
User avatar
Status: Rising GMAT Star
Joined: 05 Jun 2012
Posts: 133
Location: Philippines
Concentration: General Management, Finance
GMAT 1: 660 Q V
GPA: 3.22
WE: Corporate Finance (Consulting)
Followers: 6

Kudos [?]: 19 [0], given: 16

Re: In which quadrant of the coordinate plane does the point [#permalink] New post 18 Jun 2012, 00:09
Wengen wrote:
Hi Guys,

Can you please help with the following DS question

In which quadrant of the coordinate plane does the point (x, y) lie?

(1) |xy| + x|y| + |x|y + xy > 0
(2) -x < -y < |y|


I chose ans B but the right answer seems to be D - Each stmt alone is sufficient.



I know this is late but I had to give my crack on it and, of course, so other people might be able to learn from this very great DS question.

Anyway,

The rephrase of the question asks us for the signs of x and y. If we know the signs of x and y then we'll be able to determine which quadrant does (x,y) lie.

On to the statements:
Statement (1) |xy| + x|y| + |x|y + xy > 0

There are two ways of attacking this:
1. By algebra (conceptual method)
We can test four cases:

(A) x < 0 and y < 0:
xy + (-x)(y) + xy + (-x)(y) > 0
xy - xy + xy - xy > 0
0 = 0
So this doesn't satisfy the equation

(B) x > 0 and y < 0:
xy + xy + (x)(-y) + (x)(-y) > 0
xy + xy - xy - xy > 0
0 = 0
So this doesn't satisfy the equation

(C) x < 0 and y > 0:
xy + (-x)(y) + xy + (-x)(y) > 0
xy - xy + xy - xy > 0
0 = 0
So this doesn't satisfy the equation

(D) x > 0 and y > 0:
xy + xy + xy + xy > 0
4xy > 0
This satisfies the equation. We conclude that x > 0 and y > 0 or x = + and y = +, which means that point (x,y) lies in quadrant I.
Statement (1) is sufficient.

2. By plugging in numbers:
x = + 3
x = - 3
y = + 3
y = -3

(A) x = -3 and y = -3

|(-3)(-3)| + (-3)|-3| + |-3|(-3) + (-3)(-3) > 0
9 - 9 - 9 + 9 > 0
0 = 0
Doesn't satisfy the equation.

This is the same as the above method. This helps if someone is having a hard time dealing with the "theoretical" side of modulus.

Statement (2) -x < -y < |y|

We break down the equation into two
(A) -y < |y| -> for this to be true, y should be +
(B) -x < -y multiplying both sides by negative 1 we have: x > y (since we know that y is positive, for this to be true x should be true)
Therefore, we know that x and y are positive. Statement (2) is sufficient.

Hope other people could chime in on this, especially statement (2). I am not convinced with myself. HAHA!
_________________

Far better is it to dare mighty things, to win glorious triumphs, even though checkered by failure... than to rank with those poor spirits who neither enjoy nor suffer much, because they live in a gray twilight that knows not victory nor defeat.
- T. Roosevelt

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 23422
Followers: 3618

Kudos [?]: 28984 [0], given: 2874

Re: In which quadrant of the coordinate plane does the point [#permalink] New post 18 Jun 2012, 00:14
Expert's post
Re: In which quadrant of the coordinate plane does the point   [#permalink] 18 Jun 2012, 00:14
    Similar topics Author Replies Last post
Similar
Topics:
3 Experts publish their posts in the topic In the xy coordinate plane, does the point (3,4) lie on line obs23 2 15 Apr 2013, 04:03
23 Experts publish their posts in the topic In which quadrant of the coordinate plane does the point Bunuel 22 12 Nov 2009, 11:11
In the rectangular coordinate system, which quadrant, if any vksunder 7 20 Jul 2008, 18:22
In the rectangular coordinate system, which quadrant, if any iced_tea 5 11 Jul 2006, 07:48
If , on a coordinate plane, point A has the coordinates joemama142000 4 25 Dec 2005, 16:33
Display posts from previous: Sort by

In which quadrant of the coordinate plane does the point

  Question banks Downloads My Bookmarks Reviews Important topics  


cron

GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

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®.