The Best Way to Serve 20 Pies

Here's your nightly math! Just 5 quick minutes of number fun for kids and parents at home. Read a cool fun fact, followed by math riddles at different levels so everyone can jump in. Your kids will love you for it.

The Best Way to Serve 20 Pies

March 19, 2020

When we picture a pie, we almost always think of a circle. But these fine folks figured out how to bake a “pie-cosahedron” — that is, an icosahedron, or 20-sided shape, made of pie! They cut and bent their own triangle-shaped pie tins out of metal. Then they made pecan pie, changing the recipe to be less drippy and gooey so the upside-down pies on the bottom wouldn’t fall apart. They then baked the 20 triangle pies, and used magnets to hold all the tins together in this shape, with the pies still inside. The question is, how many people does this geo-dessert feed?

Wee ones: If your pecan pie recipe uses flour, sugar, butter, pecans and a pinch of salt, how many ingredients does it use?

Little kids: How many triangles come together at each vertex (corner) of the icosahedron?  Bonus: If you eat 1 pie from this 20-sided shape all by yourself, how many are left?

Big kids: Which will serve more people, 9 of those pies cut into 5 slices each, or 8 of those pies cut into 6 slices each?  Bonus: If every pie has 3 sides, but every edge of the icosahedron (line between triangles) is shared by 2 pies…how many edges does the shape have?




Wee ones: 5 ingredients.

Little kids: 5 triangles.  Bonus: 19 pies left.

Big kids: The 8 pies cut into 6 apiece. That gives you 48 slices, while the 9 pies give you just 45. Bonus: 30 edges. The 20 faces have 60 sides all together when they’re laid flat and not touching…then when brought together, every pair of sides makes just 1 edge in the final dessert.

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About the Author

Laura Overdeck

Laura Overdeck

Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.

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