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Is x greater than y?

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Is x greater than y?

by bluementor » Mon Jul 21, 2008 7:23 am
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?

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by adnanbbukhari » Mon Jul 21, 2008 8:27 am
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
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by cubicle_bound_misfit » Mon Jul 21, 2008 9:02 am
suppose x = -1 and y = -1

then x>2y but x !> y

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by bluementor » Tue Jul 22, 2008 1:50 am
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...
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by bluementor » Tue Jul 22, 2008 2:02 am
I've got it now! Thanks for the help.
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by cubicle_bound_misfit » Tue Jul 22, 2008 10:06 pm
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?


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