Playing with shapes
(A puzzle for early grades)
Cut a square from a large index card. (We used 5 in. by 8 in. index cards, so our
square was 5 in. by 5 in.)
Using a compass, find a point C such that the
triangle ACB is equilateral.
Connect point C with straight lines to the four
vertices of the square. Cut the square into four triangles, and you have a
four-piece puzzle.
Activities.
1. How many different polygons can you form
from these pieces? (Rule: The whole edge
of one piece must match the whole edge of another piece.)
2. Measure the lengths of the edges. (|CD| =
|CE|, and all others are equal.)
3. Figure out the angles, and then measure
them ABC is an equilateral triangle,
so its angles measure 60 degrees. So
angle CAD is 30 degrees. But |CA| = |DA|, so angle ACD = (180 -30)/2 = 75
degrees. Finally, CDE is 90 - 75 = 15
degrees, and DCE is 180 - 15 - 15 = 150 degrees.)