Coral reefs can be crocheted. The atmosphere can be knit. And a stop sign can be folded into a pair of pants. Welcome to the intersection of math and handicraft. Unexpectedly, handicraft in general, ...

Start with a deck of cards. Before the trick, sneak a peek at the 10th card in the deck. Memorize it. Ask your volunteer to add the first and second digit of their number together. For instance, if he ...