Craft & Design Science
Math Monday: Make a Ball of Money

By George Hart for the Museum of Mathematics


The diameters of US quarters and pennies are very close to the ratio needed to make a truncated icosahedron, i.e., a soccer ball in the US or a football elsewhere. Copper pennies take the place of the usually black pentagons and quarters take the place of the usually white hexagons, so even the colors work out. This ball was soldered together by Cory Poole.

Puzzle: Can you work out what it cost before looking at the answer found here?

See all of George Hart’s Math Monday columns


Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. And he has a new best-of writing collection and “lazy man’s memoir,” called Borg Like Me.

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