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coordinate

by sud21 » Thu Jan 12, 2012 9:30 am
A line in x-y coordinate system goes through the origin and point (a,b), is a < b?
1) slope < 0
2) a < 0
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Source: — Data Sufficiency |
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by avik.ch » Thu Jan 12, 2012 8:52 pm
For a line passing through the point (0,0) and (a,b), the slope is given by

m = (b-0)/(a-0) = b/a

1. slope < 0 : m<0 : b/a <0
- b is nagative, or
- a is nagative.
insufficient.

2. a<0 , we dont know the value of B.

combining both : a<0 so b > 0 and hence b>a, sufficient.



Hope this helps !!
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by sam2304 » Thu Jan 12, 2012 9:25 pm
Check Image - Self explanatory

Combining 1 & 2. a,b is in 2nd quadrant where a is -ve and b is +ve so a < b.
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by ArunangsuSahu » Thu Jan 12, 2012 9:36 pm
Think about the Gradient rule of COORDINATE GEOMETRY:

passes through origin so m=a/b= 1 or -1

Statement 1:

Slope <0

from the above either a< 0 or b<0..So INSUFFICIENT

Statement 2:
a< 0

Case I: b<0 => m=a/b=1
Case II: b >0 => m=a/b=-1

INSUFFICIENT

Combining (1) and (2)
a/b < 0(=-1) and a< 0 so b >0

a<b

SUFFICIENT

(C) is the Choice
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