2 math questions from BB 2nd edition

cortana431
Fri, 29 Jul 2011 11:26:36 +0000

The two overlapping triangles are triangles ADF and BCE. Because DE=EF=10, the side length of triangle ADF is 10+10=20. Let the point of intersection of lines BE and AD be G. Triange GDE is also and equilateral triangle because it was formed by two overlapping equilateral triangles and it has a side length of 10 (DE=10). Because AD=20, we want AG, which is half of AD or 10. Similarly, BG=10. Thus, our answer is CD+DE+EF+FA+AG+GB+BC=10+10+10+20+10+10+20= 90