lines

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 131
Joined: Tue Aug 05, 2008 3:28 pm
Thanked: 2 times

lines

by mariah » Sun Jan 15, 2012 5:05 am
Line m and n are perpendicular to each other. Is the abscissa of their intersection -1?
1) The slope of m=1/7
2) n passes through point (0,4)

oa E

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Sun Jan 15, 2012 5:15 am
mariah wrote:Line m and n are perpendicular to each other. Is the abscissa of their intersection -1?
1) The slope of m=1/7
2) n passes through point (0,4)

oa E
Abscissa means the x-coordinate.

(1) Slope of m = 1/7 and lines m and n are perpendicular means that the product of their slopes should be -1.
So, slope of n = -7 but the x-coordinate of the intersection may or may not be -1; NOT sufficient.

(2) n passes through point (0,4) but we cannot find the point of intersection of the 2 lines using this info; NOT sufficient.

Combining (1) and (2), equation of line n is (y - 4) = -7(x - 0) but we don't know the equation of line m; NOT sufficient.

The correct answer is E.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/

Master | Next Rank: 500 Posts
Posts: 382
Joined: Thu Mar 31, 2011 5:47 pm
Thanked: 15 times

by ArunangsuSahu » Sun Jan 15, 2012 6:48 am
Gradient of the line n=-7=(4-a)/(0-b)

But (a,b) the point of intersection not known

so (E)

User avatar
Legendary Member
Posts: 626
Joined: Fri Dec 23, 2011 2:50 am
Location: Ahmedabad
Thanked: 31 times
Followed by:10 members

by ronnie1985 » Sun Jan 15, 2012 8:33 pm
S1:-
The slope of m is 1/7 means:-
m: y = (1/7)x+c1 and n: -7x+c2. Since no other info is available it cannot be solved for x or y
Not Sufficient

S2:-
n: y = nx+4, nothing else can be figured out.

Comb:-
m: y = (1/7)x+c1
n: y = -7x+4
Since C1 not known, it cannot be said that the x value of intersection is -1.

(E) is answer.
Follow your passion, Success as perceived by others shall follow you