I was surprised at how simple this is, as it confused the hell out of me at first. Okay, the two triangles made by those lines, ABC and ADE, are similar because you can tell that their angles are the same (laws of geometry). Pretend you bisected angle A dividing the triangles in half and folded the circle--you can see this. Segment BD corresponds with AD, AC with AE, and BC with DE. AB = 4 and AD = 6. The ratio of these segments is 6/4. To find out what DE is, multiply BC's length by 6/4:
6 * 6/4 = 36/4 = 9.
The answer is D.
Geometry circle traingle
This topic has expert replies
Source: Beat The GMAT — Problem Solving |
-
vishubn
- Legendary Member
- Posts: 574
- Joined: Sun Jun 01, 2008 8:48 am
- Location: Bangalore
- Thanked: 28 times
Damn 
brb was a little fast !!
Yaa similar triangles is wat is tested here
Ya same approach ! isntead i knew the ratio ! so each side multipled by th 3/2
Vishu
brb was a little fast !!
Yaa similar triangles is wat is tested here
Ya same approach ! isntead i knew the ratio ! so each side multipled by th 3/2
Vishu
KILL !! DIE !! or BEAT my FEAR !!! de@D END!!
-
brb588
- Senior | Next Rank: 100 Posts
- Posts: 61
- Joined: Mon Nov 17, 2008 11:35 pm
- Thanked: 6 times
- Followed by:1 members
Hi. BE does appear to be the diameter, but it wouldn't matter if it was or not. Whenever two lines cross, or make an X, the angles opposite of each other are the same. I tried to find something online to back me up and this is the best I could do: https://homepages.ius.edu/rriehm/T103/T1 ... .3sp03.pdf. Angles BAC and DAE have to be the same.raunekk wrote:is BE diameter??
wats d source of the question??
can you pls elaborate on this...are similar because you can tell that their angles are the same (laws of geometry)
As for the other angles, you just have to look at the diagram and visualize two similar triangles. I'm sure there is some super technical explanation, but in a nutshell, BC and DE have to mirror each other at point A. Therefore, the triangles are similar. Look at what I attached. Imagine if circle was folded in half at the red line. The triangles have the exact same angles, and are similar.
- Attachments
-
-
brb588
- Senior | Next Rank: 100 Posts
- Posts: 61
- Joined: Mon Nov 17, 2008 11:35 pm
- Thanked: 6 times
- Followed by:1 members
vishubn wrote:Damn
brb was a little fast !!
Yaa similar triangles is wat is tested here
Ya same approach ! isntead i knew the ratio ! so each side multipled by th 3/2
Vishu
I just got through studying and wanted to hit up the forum to see if I could try a problem out.
-
ronniecoleman
- Legendary Member
- Posts: 546
- Joined: Sun Nov 16, 2008 11:00 pm
- Location: New Delhi , India
- Thanked: 13 times
There is a theorem:
angles on the same arc are equal..
like wise prove that two triangles are similar <abc <ade
use similar theorem and get the answer..
Point blank point simple!
angles on the same arc are equal..
like wise prove that two triangles are similar <abc <ade
use similar theorem and get the answer..
Point blank point simple!
Admission champion, Hauz khaz
011-27565856
011-27565856
