GMAT Prep

Guest · Posted: Fri Sep 07, 2007 11:19 pm Post subject: GMAT Prep

Hi all,

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Just in case if the image doesn't show,

Are x and y both positive?

1. 2x - 2y = 1
2. x/y >1

I thought the answer is E.
From stmt 1 we know that x - y = 1/2 and from stmt 2 x > y
When we combine both, we can still have x as positive and y as negative, such as when x = 1/4 and y = -1/4. x > y and x - y = 1/2.

Please explain whether my error is since the correct answer is C.

agps · Posted: Sat Sep 08, 2007 3:37 am Post subject:

from 1) x and y are either both positive and x>y or x and y have different signal and x> 0. more than 1 possible answer, insufficient.

from2) both x and y have the same signal negative or positive we don't know, insufficient

combining both, from 1) x is always positive and from 2) x and y both have the same signal, so both are positive. answer C

Jameschan168 · Posted: Sun Sep 09, 2007 4:19 pm Post subject:

Can someone explain what happens after we combine both stmts? I'm still a little confused with agps's explanation. Thanks.

ri2007 · Posted: Sun Sep 09, 2007 10:02 pm Post subject:

Jameschan168

A suggestion when u find it diff to relate to variables plug in values.

Take the question in discussion -

Statement 1 gives X>Y

So X can be 6 and Y can be 3 or X can be -3 and Y can be -6

Statement 2 gives X/y >1

If you look at the statement alone again X can be 6 and Y can be 3 or X can be -3 and Y can be -6

But if you combine the statement you know X > y so for x/y to be > 1 they will have to be positive. IF they were negative X/y would be a fraction and so less than 1

kajcha · Posted: Mon Sep 10, 2007 10:41 am Post subject:

Stmt 1 - both, x and y, can be positive or negative. NOT SUFF

Stmt 2 - both will be negative or positive. NOT SUFF

Together - from stmt 2 |x|>|y| and stmt 1 satisfies only when both are positive. So SUFF

Ans C

gmatguy16 · Posted: Mon Sep 10, 2007 12:20 pm Post subject:

ans is correct e:
you guys did not consider x=-1/2 and y=-1.

gmatguy16 · Posted: Mon Sep 10, 2007 12:21 pm Post subject:

rather x=-1 and y=-1/2

kajcha · Posted: Mon Sep 10, 2007 1:40 pm Post subject:

Jameschan168 · Posted: Tue Sep 11, 2007 11:50 am Post subject:

Thanks ri2007.