Coordinate Geometry.

This topic has expert replies
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Thu Sep 08, 2016 7:02 am
Pawan Ramnani wrote:What is the area inscribed by the lines y =1, x = 1, y = 6-x on an xy-coordinate plane?

a) 8
b) 10
c) 12
d) 14
e) 18

Answer is 8.
When posting questions, please use the spoiler function to hide the correct answer. This will allow others to attempt the question without seeing the final answer.

First, let's graph the lines y = 1 and x = 1
Image

At this point, we need to find the points where the line y = 6-x INTERSECTS the other two lines.

For the vertical line, we know that x = 1, so we'll PLUG x = 1 into the equation y = 6-x to get y = 6-1 = 5
Perfect, when x = 1, y = 5, so one point of intersection is (1,5)

For the horizontal line, we know that y = 1, so we'll PLUG y = 1 into the equation y = 6-x to get 1 = 6-x. Solve to get: x = 5
So, when y = 1, x = 5, so one point of intersection is (5,1)

Now add these points to our graph and sketch the line y = 5-x
Image

At this point, we can see that we have the following triangle.
Image
The base has length 4 and the height is 4
Area = (1/2)(base)(height)
= (1/2)(4)(4)
= 8

Answer: A
Brent Hanneson - Creator of GMATPrepNow.com
Image

User avatar
Legendary Member
Posts: 2663
Joined: Wed Jan 14, 2015 8:25 am
Location: Boston, MA
Thanked: 1153 times
Followed by:128 members
GMAT Score:770

by DavidG@VeritasPrep » Thu Sep 08, 2016 7:38 am
For another good "area on the coordinate plane" question, see here: https://www.beatthegmat.com/coordinate-p ... 63268.html
Veritas Prep | GMAT Instructor

Veritas Prep Reviews
Save $100 off any live Veritas Prep GMAT Course