WASHINGTON STATE MATHEMATICS COUNCIL
1999 MIDDLE SCHOOL MATH OLYMPIAD
EIGHTH GRADE GEOMETRIC SENSE
Make sure you include proper units in your answer!

8

 

1. The figure ABCDEF at right is made up of two congruent trapezoids, ABCF and DEFC, where trapezoid ABCF has been rotated to create trapezoid DEFC. Find the area of the figure ABCDEF.

 

 

 

 

2. How many equilateral triangles of any size can be made using the "pegs" on the triangular geoboard at right? Count triangles in different positions on the board as different triangles. All of the pegs are equally spaced.

 

 

 

3. Triangles A, B, and C are similar triangles. Write a sentence stating how the perimeter of triangle B compares in measure with the perimeter of triangle C.

 

 

 

 

4. On the answer sheet, draw the figure that would result when the figure at right has been transformed by:

  • first rotating the figure about the point R in a clockwise direction through an angle of 90 degrees, and

  • second, reflecting the newly positioned figure across the "reflection line" shown.

 

 

 

5. Determine what percent the area of square A is of the area of circle B, and what percent the area of circle B is of the area of square C. To the nearest tenth of a percent, what is the difference in the percents?