Just as 13 breaks up nicely as the sum of 8 and 5, so too does the (volume of a) cylinder break up nicely as the sum of a cone and hemisphere, a fact we have seen demonstrated at previous Gatherings in vivid ways. But the one-diagram proof of this…

There are 52 cards in a standard deck of playing cards: four suits of 13 cards each. To design a deck of cards, one needs to establish the four suits, each with its own symbol and/or concept, and find a logic for generating the 13 cards in each suit,…

A small booklet of 20 math puzzles that involve the element of surprise. Some appear to lack sufficient information to solve; others run counter to one's intuition as to what the answer should be.

Physical physics toy gift for the exchange: A craft kit with all parts needed to crate a tiny kinetic sculpture based on the physics of equilibrium, magnetic force, and angular momentum.

This pair of unique dice consists of a 13-sided die with both numbers and face-card labels for J, Q, K, and A, along with a 4-sided die with the standard playing card suits.