If x and y are integers such that x < y < 0, what is x

Expert replies

zenithexe: Senior | Next Rank: 100 Posts; Posts: 49; Joined: Tue Jun 16, 2009 8:20 pm; Thanked: 5 times

by zenithexe » Thu Jul 02, 2009 11:47 pm

If x and y are integers such that x < y < 0, what is x – y?

(1) (x + y)(x – y) = 5
(2) xy = 6

I have no idea how to solve this one, any help is appreciated. Thanks

Like this post

Source: Beat The GMAT — Data Sufficiency | Thu Jul 02, 2009 11:47 pm

tohellandback: Legendary Member; Posts: 752; Joined: Sun May 17, 2009 11:04 pm; Location: Tokyo; Thanked: 81 times; GMAT Score:680

by tohellandback » Fri Jul 03, 2009 12:12 am

IMO A
1)( x + y)(x – y) = 5
possibilities:
(x+y)=1 ,(x-y)=5- rejected because x and y are negative
(x+y)=5 ,(x-y)=1, rejected for the same reason

(x+y)=-1 ,(x-y)=-5, if x+y=-1 x=-y-1, now x has to be negative. for any value of y<0, it is impossible. so rejected
(x+y)=-5 ,(x-y)=-1. SUFFICIENT

2)xy=6. x and y have to be negative. so one of them is -2 and other is -3 but we need to know which one is what. INSUFF

Last edited by tohellandback on Fri Jul 03, 2009 12:25 am, edited 1 time in total.

The powers of two are bloody impolite!!

Like this post

zenithexe: Senior | Next Rank: 100 Posts; Posts: 49; Joined: Tue Jun 16, 2009 8:20 pm; Thanked: 5 times

by zenithexe » Fri Jul 03, 2009 12:22 am

wow, never thought I'd see a guy/gal from Tokyo on this site. Its nice to know there is someone else studying for Gmat in Japan.

Thanks for the solution, I get it now.

Like this post

tohellandback: Legendary Member; Posts: 752; Joined: Sun May 17, 2009 11:04 pm; Location: Tokyo; Thanked: 81 times; GMAT Score:680

by tohellandback » Fri Jul 03, 2009 12:24 am

never thought I'd see a guy/gal from Tokyo on this site

umm, why not??

The powers of two are bloody impolite!!

Like this post

zenithexe: Senior | Next Rank: 100 Posts; Posts: 49; Joined: Tue Jun 16, 2009 8:20 pm; Thanked: 5 times

by zenithexe » Fri Jul 03, 2009 12:29 am

Coz I did search for Tokyo (or was it Japan) on "Let's meet up" section and I found none.

I guess I should pm for this kind of stuff, it's getting off the topic.

Like this post

benissleeping: Senior | Next Rank: 100 Posts; Posts: 36; Joined: Tue May 05, 2009 1:20 am; Thanked: 2 times

by benissleeping » Fri Jul 03, 2009 12:34 am

This was my thinking on the Q:

(1) Multiply out x^2 - y^2 = 5
Just by looking at this you can see it solves for x=-4 and y=-3 (16-9=5)
and x=-3 and y=-2 (9-4=5)

x-y = -1

(2) xy=6
x could be -6 and y -1 or x -3 and y -2. NS

So A

Like this post

zenithexe: Senior | Next Rank: 100 Posts; Posts: 49; Joined: Tue Jun 16, 2009 8:20 pm; Thanked: 5 times

by zenithexe » Fri Jul 03, 2009 12:54 am

benissleeping wrote:This was my thinking on the Q:

(1) Multiply out x^2 - y^2 = 5
Just by looking at this you can see it solves for x=-4 and y=-3 (16-9=5)
and x=-3 and y=-2 (9-4=5)

Thanks!
just out of curiosity how do you quickly come up with the numbers (X^2=16, Y^2=9)? and it there a way to be sure that those numbers are only numbers capable of satisfying the clause? I wish I could do that.

Like this post

tryin700: Junior | Next Rank: 30 Posts; Posts: 15; Joined: Sun Jul 13, 2008 6:23 pm

by tryin700 » Fri Jul 03, 2009 1:10 am

Is it A

Given x<y<1

1) (x + y)(x – y) = 5

RHS = +5

so 2 combination are possible

-5X-1 or -1X-5

this means x=-3 and y=-2

SUFF

2) xy=6
possible cases -1 and -6 or -3 or -2

INSUFF

Hence A

Like this post

ogbeni: Master | Next Rank: 500 Posts; Posts: 186; Joined: Sat Sep 02, 2006 7:50 pmFollowed by: 1 member; Thanked: 10 times

by ogbeni » Thu Jul 09, 2009 9:55 am

Why is statement 1 sufficient when (X-Y) could be either -1 or -5? I eliminated statement 1 based on those 2 possibilities.

Look forward to getting an explanation! Thnx

Like this post

matanga: Junior | Next Rank: 30 Posts; Posts: 12; Joined: Tue Jul 07, 2009 1:57 pm; GMAT Score:650

by matanga » Thu Jul 09, 2009 1:53 pm

ogbeni wrote:Why is statement 1 sufficient when (X-Y) could be either -1 or -5? I eliminated statement 1 based on those 2 possibilities.

Look forward to getting an explanation! Thnx

Because you have 2 negative numbers, and, since y>x, when you subtract y from x, you are technically adding a value to x to make it closer to 0. Had the question not stated y was negative, then your logic would have been correct.

Hope this helps !

Like this post

ogbeni: Master | Next Rank: 500 Posts; Posts: 186; Joined: Sat Sep 02, 2006 7:50 pmFollowed by: 1 member; Thanked: 10 times

by ogbeni » Thu Jul 09, 2009 2:13 pm

Oh i get it now. The fact that x<y<0 limits the possibilities of x and y to x = -3 and y = -2.

My goodness!! With the time pressure on the GMAT and without considering values for x and y, I just reasoned that the values of (x+y) x (x-y) could be -5,-1 or -1, -5 therefore eliminate - ARRGHHHH I hate that!!!!!!! lol

Thanks for clarifying

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review