BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Coordinate Geometry

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 13
Joined: Fri Jan 07, 2011 10:14 pm
Thanked: 2 times
Followed by:1 members

Coordinate Geometry

by koby_gen » Wed May 11, 2011 10:51 am
In the xy-coordinate plane, line I1 and line I2 intersect at the point (-2,5). Is the product of their slopes negative ?

(1) The product of the x-intercepts of lines I1 and I2 is negative.

(2) The product of the y-intercepts of lines I1 and I2 is positive.
Top
Source: — Data Sufficiency |
Master | Next Rank: 500 Posts
Posts: 118
Joined: Wed Mar 16, 2011 12:51 am
Location: New Delhi, India
Thanked: 12 times
Followed by:1 members

by pankajks2010 » Wed May 11, 2011 6:56 pm
IMO C.

Please can you share the OA.

Thanks!!
Top
Senior | Next Rank: 100 Posts
Posts: 57
Joined: Fri Jan 14, 2011 10:01 am
Thanked: 10 times

by djiddish98 » Thu May 12, 2011 7:29 am
FYI - I'm bad at these coordinate geo problems.

The way I'm reading it, we want to know if only 1 of the slopes are negative (thus the product will be negative). So the question is, are the lines going in the same direction or are they going in opposite directions?

Statement 1 - This tells us that 1 x intercept is negative and 1 x intercept is positive. If the lines intersect at (-2,5), and an x intercept is positive, I believe that means that 1 slope is negative.

since x intercept is when y = 0. If (-2,5) is a point on a line and x is positive when y = 0, that means y is decreasing as x is increasing or negative slope.

I think this is sufficient

Statement 2 - Tells us that both Y intercepts are positive or negative. However, a negative sloping line could have a positive Y intercept or it may not. If -2,5 is a point, then a slope of -1/2 would have a y intercept at 0,4. a slope of 1/2 would have a y intercept at 0,6. I believe we can construct the same with negative Y intercepts. Therefore, we don't know if only 1 slope is negative.

Insufficient.

IMO: A
Top
User avatar
Legendary Member
Posts: 516
Joined: Mon Nov 02, 2009 6:42 am
Location: Mumbai
Thanked: 14 times
Followed by:1 members
GMAT Score:710

by ankurmit » Thu May 12, 2011 7:48 am
IMO A is answer.
--------
Ankur mittal
Top
Master | Next Rank: 500 Posts
Posts: 183
Joined: Sat Apr 16, 2011 11:29 am
Thanked: 7 times
Followed by:2 members

by Chaitanya_1986 » Thu May 12, 2011 10:20 am
Can any one explain this by Graphical approach????
Top
Senior | Next Rank: 100 Posts
Posts: 57
Joined: Fri Jan 14, 2011 10:01 am
Thanked: 10 times

by djiddish98 » Thu May 12, 2011 11:49 am
I think my original answer was wrong, because I ignored the potential for a line to have a slope of -5. If 1 line is -5 and the second line is -1/2, then you can have 2 negative slopes in addition to a negative x int and positive x int.

I'm switching to C - if both of them are crossing the Y axis at positive or negative, the only way they can have a negative x intercept and a positive x intercept is if they are sloping in opposite directions (I think).
Top
User avatar
Senior | Next Rank: 100 Posts
Posts: 57
Joined: Tue Apr 19, 2011 7:39 pm
Location: Singapore
Thanked: 6 times
Followed by:2 members

by abhi0697 » Mon May 16, 2011 6:36 am
IMO C
Top
User avatar
Legendary Member
Posts: 516
Joined: Mon Nov 02, 2009 6:42 am
Location: Mumbai
Thanked: 14 times
Followed by:1 members
GMAT Score:710

by ankurmit » Mon May 16, 2011 6:55 am
pls post OA
--------
Ankur mittal
Top
Post new topic Post Reply
• Page 1 of 1