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Polyhedra lovers are fond of certain compound shapes, such as this symmetric arrangement of five concentric regular tetrahedra. If you like to make things in wood, it’s a natural challenge to cut some plywood, bevel the edges, and screw or glue together a giant geometric model. Here is Dale Seymour with his compound of five tetrahedra.

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One of the five is made of four large triangles and serves as an inner support to which the facets for the other four tetrahedra were added. Below you can see the facets before assembly.

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In a similar style, Dale made this colorful compound of five concentric cubes.

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See all of George Hart’s Math Monday columns