Problem:
In square ABCE,AF=2FE and CD=2DE. What is the ratio of the area of β³BFD to the area of square ABCE?
Answer Choices:
A. 61β
B. 92β
C. 185β
D. 31β
E. 207β
Solution:
Because the answer is a ratio, it does not depend on the side length of the square. Let AF=2 and FE=1. That means square ABCE has side length 3 and area 32=9 square units. The area of β³BAF is equal to the area of β³BCD=21ββ
3β
2=3 square units. Triangle DEF is an isosceles right triangle with leg lengths DE=FE=1. The area of β³DEF is 21ββ
1β
1=21β square units. The area of β³BFD is equal to the area of the square minus the areas of the three right triangles: 9β(3+3+21β)=25β. So the ratio of the area of β³BFD to the area of square ABCE is 925ββ=185β.
Answer: Cβ.
The problems on this page are the property of the MAA's American Mathematics Competitions