Math Monday: Tie Your Bagel in a Knot!
DECEMBER 21, 2009

by George Hart

Our post about how to cut a bagel into two linked halves was so popular that we thought we’d show you some more mathematical food play: how to knot a bagel. (This also works with inner tubes, but they are too chewy.)
The bread of a bagel forms a simple loop, which mathematicians call “the unknot”. But there are two easy ways to cut a bagel into a simple overhand knot, or “trefoil” knot. Above is a what mathematicians call “the (2,3)-torus knot toasted with cream cheese.”
Another is the (3,2)-torus knot, shown here with a string following the path of the bagel, to make clear how it is a trefoil knot. Detailed instructions for both these breakfasts are shown here.

This article first appeared on Make: Online, December 21, 2009.

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