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Source: — Data Sufficiency |
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by iamseer » Sat May 08, 2010 10:51 pm
from 1:
y>0
therefore 3y >0
-2x>3y therefore -2x>0
therefore x has to be negative
Sufficient

from 2:
2x+5y=20
x+2.5y=10
x=10-2.5y
If y>4, x is negative
if y<4, x is positive
if y=4, x is zero
Not Sufficient

IMO answer A
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by Rahul@gurome » Sat May 08, 2010 10:55 pm
If -2x > 3y, then x<(-3/2)*y.
Consider (1) alone.
y > 0.
So (-3/2)*y < 0.
Since x<(-3/2)*y and (-3/2)*y < 0, we have x < 0.
So x is negative.
Or (1) is sufficient.

Consider (2) alone.
If 2x+5y-20 = 0, then 3y = {(20 - 2x)/5}*3
So -2x > {(20 - 2x)/5}*3
Or -10x > 60-6x
Or 4x< -60
Or x < -15.
So x is negative.
Or (2) is sufficient.

The correct answer is (D).
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by iamseer » Sat May 08, 2010 10:59 pm
Rahul@gurome wrote: Consider (2) alone.
If 2x+5y-20 = 0, then 3y = {(20 - 2x)/5}*3
So -2x > {(20 - 2x)/5}*3
Or -10x > 60-6x
Or 4x< -60
Or x < -15.
So x is negative.
Or (2) is sufficient.

The correct answer is (D).
Thanks Rahul.
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by iamseer » Sat May 08, 2010 11:05 pm
iamseer wrote:from 1:
y>0
therefore 3y >0
-2x>3y therefore -2x>0
therefore x has to be negative
Sufficient

from 2:
2x+5y=20
y=(20-2x)/5
3y= (60-6x)/5
-2x > (60-6x)/5
-10x > 60 - 6x
-4x>60

therefore x is negative.
Sufficient.

answer D

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