Data Sufficiency

Is x greater than y?

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

My answer was D, but the OA is B. Can someone please explain my error here?

Source: Free Downloadable GMAT Practice Test Questions , TestPrepReview.com

1) X>2y is not sufficeint as the inequality reverses for -ve numbers
2) x-y > 0 can be simplified to x>y and is sufficuient

suppose x = -1 and y = -1

then x>2y but x !> y

regards,

thanks for your replies...but i'm still not clear with this...

adnanbbukhari,

1) X>2y is not sufficeint as the inequality reverses for -ve numbers
2) x-y > 0 can be simplified to x>y and is sufficuient

statement 1 simply says that x is greater than twice of y, regardless if its positive or negative. why would the inequality reverse for -ve numbers?


cubicle bound misfit,

suppose x = -1 and y = -1

then x>2y but x !> y

why would you pick x=y=-1 when you are trying to evaluate if x>y? should you not pick two different numbers for x and y?


I guess there is a very simple explanation to this which is simply not sinking in me. please help...

I've got it now! Thanks for the help.

Hi Bluementor,

The premise given is x>2y we have to see whether it is valid only for those x which is greater than y? what if for some x which is less or equal to y the ineqaulity will hold true?


regards,