DS Coordinate Geometry

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 214
Joined: Wed Nov 14, 2007 6:30 am
Thanked: 15 times

DS Coordinate Geometry

by sujaysolanki » Fri Dec 07, 2007 8:53 pm
Could someone please explain how both are sufficient in calculating the slope ..
Attachments
19.JPG

User avatar
Community Manager
Posts: 789
Joined: Sun Jan 28, 2007 3:51 pm
Location: Silicon valley, California
Thanked: 30 times
Followed by:1 members

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.

Newbie | Next Rank: 10 Posts
Posts: 5
Joined: Mon Jan 05, 2009 3:16 pm

by wrtau23 » Wed Jan 07, 2009 2:46 pm
Can you elaborate on combining the equations?

User avatar
Legendary Member
Posts: 2134
Joined: Mon Oct 20, 2008 11:26 pm
Thanked: 237 times
Followed by:25 members
GMAT Score:730

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
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"