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DS Coordinate Geometry

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Source: — Data Sufficiency |
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by jayhawk2001 » Sat Dec 08, 2007 9:51 am
Let eqn of line n: y = m1x + c1
Eqn of line p: y = m2x + c2

1 - insufficient. we just have
1 = 5m1 + c1
1 = 5m2 + c2

2 - insufficient.
we just know c1 > c2

combining the two we can see that m2 > m1. Hence sufficient.
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by wrtau23 » Wed Jan 07, 2009 2:46 pm
Can you elaborate on combining the equations?
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by logitech » Wed Jan 07, 2009 4:17 pm
jayhawk2001 wrote:Let eqn of line n: y = m1x + c1
Eqn of line p: y = m2x + c2

1 - insufficient. we just have
1 = 5m1 + c1
1 = 5m2 + c2

2 - insufficient.
we just know c1 > c2

combining the two we can see that m2 > m1. Hence sufficient.
Multiply the first equation with -1 and add with the second equation

-1 = -5m1-c1
1 = 5m2+c2

+
----------------------

0 = 5(m2-m1) + c2-c1

SO,

5(m2-m1) = c1-c2 from the second statement we know that c1>c2 so c1-c2>0


5(m2-m1) > 0

m2-m1 > 0

m2>m1

TATAMM!!

You can easily solve this question on XY plane without calculations.
LGTCH
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