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Materials
The Geometry Center's icosahedron was made from 1/8 inch foamboard,
which is available at most art supply stores. We used white foamboard
and had the students color and decorate each panel. The amount of
foamboard you need depends on the edge length for your icosahedron.
Foamboard comes in rectangles of length 32x40 inches.
Because foamboard costs approximately $5 per sheet,
it is convenient to plan the side length of your icosahedron to
maximize the number of triangles that will fit on each sheet. This
makes a nice exercise for the students. For example:
 The Geometry Center cut out each triangular panel from a
32x40 inch rectangular pieces of foamboard.
Three possible ways to cut the triangle are
shown in Figure 2.
What is the maximum edge length
of each triangle? Does your answer change if we also want to reduce
the amount of cutting that we are required to do?
You will also need an Xacto knife ($2$5), a onehole paper punch, and
"twist ties" (e.g., those used to close kitchen garbage bags).
Hardware stores often have packs of 100 ties for about $1. You may
also want materials for coloring; we used assorted magic markers. A
yardstick, meterstick, or some other straightedge is also useful.
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