co-ordinate geometry

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 423
Joined: Fri Jun 11, 2010 7:59 am
Location: Seattle, WA
Thanked: 86 times
Followed by:2 members

co-ordinate geometry

by srcc25anu » Mon Mar 28, 2011 5:48 am
A line with the equation y = px + q is reflected over the line y = x. Is the reflection of this line parallel to the line y = mx + n?

(1) m = p + 2

(2) m = 3p

OA C
Source: — Data Sufficiency |

Legendary Member
Posts: 857
Joined: Wed Aug 25, 2010 1:36 am
Thanked: 56 times
Followed by:15 members

by AIM GMAT » Mon Mar 28, 2011 6:15 am
Hey anu,

Whats the source of this question ? Is it GMAT question or CAT one ... coz its pretty annoying ... !!!
Thanks & Regards,
AIM GMAT

Master | Next Rank: 500 Posts
Posts: 423
Joined: Fri Jun 11, 2010 7:59 am
Location: Seattle, WA
Thanked: 86 times
Followed by:2 members

by srcc25anu » Mon Mar 28, 2011 6:24 am
its from grockit.com

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 » Mon Mar 28, 2011 7:39 am
srcc25anu wrote:A line with the equation y = px + q is reflected over the line y = x. Is the reflection of this line parallel to the line y = mx + n?

(1) m = p + 2

(2) m = 3p

OA C
Image

Slope of line y = px + q is p and slope of line y = mx + n is m.
(1) m = p + 2 implies there is just one equation and 2 variables. Until we know the values of m and p, we cannot say whether reflection of y = px + q is parallel to the line y = mx + n. So, (1) is NOT SUFFICIENT.

(2) m = 3p again implies there is just one equation and 2 variables. Until we know the values of m and p, we cannot say whether reflection of y = px + q is parallel to the line y = mx + n. So, (2) is NOT SUFFICIENT.

Combining (1) and (2), 3p = p + 2 implies p = 1 and m = 3. So, now we can find the angle that each of the two lines make with x -axis. Hence, combining the statements is SUFFICIENT to answer the question.

The correct is C.
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/