XY plane

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 31
Joined: Sat Aug 23, 2008 8:23 pm
Location: Toronto
Thanked: 1 times
GMAT Score:610

XY plane

by ebehboud » Sat May 02, 2009 11:46 am
Lines n and p lie in xy plane. Is slope of line n less than slope of line p?
a. Lines n and p intersect at (5, 1)
b. Y-intercept of line n is greater than y intercept of line p
Source: — Data Sufficiency |

Junior | Next Rank: 30 Posts
Posts: 28
Joined: Wed Apr 15, 2009 11:35 pm
Thanked: 1 times

by mixpanda » Sat May 02, 2009 3:21 pm
I think the answer is C - both pieces of info are needed to figure it out.

1- insufficient on its own because the info doesn't indicate in which directions each slope points. We do know, however, that they intersect, so one slop must point down and one must slope up. The one that slopes down is the one that is less, but from this info we can't tell which is n and which is p.

2 - insufficient on its own because although the y intercepts are different, the slopes could be pointing in any direction (up or down) or any degree of up or down. Even though n is located higher up on the y axis, it could be pointing down with a negative slope.

1 + 2 - together this info indicates which slope is higher and which is lower. If n intersects the y axis at a higher point than where the p line intersects this axis, and if both lines must meet at (5,1), then the n slope must be lower than the p slope. Either the n slope is pointing downwards towards (5,1) while p is pointing upwards towards (5,1), or the n slope is pointing slightly less upward toward (5,1) in comparison to the p slope

We are able to answer the question, so the answer is C.

Senior | Next Rank: 100 Posts
Posts: 31
Joined: Sat Aug 23, 2008 8:23 pm
Location: Toronto
Thanked: 1 times
GMAT Score:610

by ebehboud » Sat May 02, 2009 4:52 pm
You are correct.
thank you