Dint get this!!

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 429
Joined: Wed Sep 19, 2012 11:38 pm
Thanked: 6 times
Followed by:4 members

Dint get this!!

by [email protected] » Mon Aug 05, 2013 8:17 am
In the figure to the left, x and y are greater than or equal to 0, the vertices of triangle ABC have coordinate values as shown, and the value of AC is as shown. If x = 3, then what could be the equation of line AC
Attachments
btgcg.jpg
Source: — Problem Solving |

User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Mon Aug 05, 2013 8:37 am
In the figure shown below, x and y are greater than or equal to 0, the vertices of triangle ABC have coordinate values as shown, and the value of AC is as shown. If x = 3, then what could be the equation of line AC?


Image

A. 4x + 3y = 8
B. 3x - 4y = 8
C. 4x - 3y = 8
D. 4x + 3y = 24
E. 3x + 4y = 24
Image

Since x=3, AB = (x+3) - x = (3+3) - 3 = 3.
Thus, ∆ABC is a 3-4-5 triangle.
Since AB=4, the y-intecept of line AC must be greater than 4.

The x-coordinate of any y-intercept is 0.
Thus, when x=0 is plugged into the correct answer choice, the resulting y value must be greater than 4.
A quick scan of the answer choices reveals that only D and E are viable.
Eliminate A, B and C.

To travel from point A to point C, we move down 4 units and to the right 3 units, implying a slope of -4/3.
Answer choice D:
4x + 3y = 24
3y = -4x + 24
y = (-4/3)x + 8.
Success! The slope = -4/3.

The correct answer is D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3