BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Isosceles Triangle Angles

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Junior | Next Rank: 30 Posts
Posts: 26
Joined: Fri Jul 17, 2015 1:09 pm
Thanked: 1 times

Isosceles Triangle Angles

by mattnyc15 » Wed Nov 04, 2015 4:04 pm
I'm confused by this questions:


Image


I understand DCB = 60, ACD= 20 and each triangle is an isosceles.

But wouldn't that the other angle is DCB 60?? and ACD 140?

I know X must be the angle on the other side too, but from here i'm confused. [/img]


OA: X= 10
Top
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 363
Joined: Sun Oct 17, 2010 3:24 pm
Thanked: 115 times
Followed by:3 members

by theCEO » Wed Nov 04, 2015 5:00 pm
mattnyc15 wrote:I'm confused by this questions:


Image


I understand DCB = 60, ACD= 20 and each triangle is an isosceles.

But wouldn't that the other angle is DCB 60?? and ACD 140?

I know X must be the angle on the other side too, but from here i'm confused. [/img]
DC = DB ; DBC = DCB = 60
BDC = 180-(DBC+DCB) = 180 - 120 = 60

AD = DC ; ACD = CAD = 20
ADC = 180 - (ACD + CAD) = 180 - 40 = 140

ADB = 360 - (ADC + BDC) = 360 - 200 = 160

BAD = ABD
BAD = (180 - ADB)/2 = (180 - 160)/2 = 10

X = 10


OA: X= 10
Top
User avatar
Junior | Next Rank: 30 Posts
Posts: 26
Joined: Fri Jul 17, 2015 1:09 pm
Thanked: 1 times

by mattnyc15 » Wed Nov 04, 2015 7:37 pm
Thanks! The 360 for the circle in the middle made it click.
Top
Post new topic Post Reply
• Page 1 of 1