parallel lines.

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 431
Joined: Sat Jan 10, 2009 9:32 am
Thanked: 16 times
Followed by:1 members

parallel lines.

by kanha81 » Mon Jun 08, 2009 6:45 am
From the attached figure, find the angle ACD.

A. 100
B. 90
C. 80
D. 70
E. cannot be determined from the information

I got this answer right, but did some calculations. I also found a much simpler way to determine the answer in much simpler way :)
Attachments
parallel lines.pdf
(6.24 KiB) Downloaded 96 times
Want to Beat GMAT.
Always do what you're afraid to do. Whoooop GMAT
Source: — Problem Solving |

Legendary Member
Posts: 752
Joined: Sun May 17, 2009 11:04 pm
Location: Tokyo
Thanked: 81 times
GMAT Score:680

by tohellandback » Mon Jun 08, 2009 6:51 am
IMO 80

join DC with AB. joining angle will be 50 because lines are parallel.

see the attachment
Attachments
soln.JPG
The powers of two are bloody impolite!!

Newbie | Next Rank: 10 Posts
Posts: 1
Joined: Thu Nov 20, 2008 7:59 am

by tompal » Mon Jun 08, 2009 7:57 am
I’m also getting 80º, but my approach was a bit different… please let me know if my thinking is correct…

Since AB||DE a straight line can be drawn form point A to Point D that would be perpendicular. With the resulting 90º angels you can calculate the interior angles of triangle ACD then subtract to get the measure of angle C, see the illustration…

What is the OE
Attachments
problem2.PNG