# Browse Items (98 total)

- Collection: G4G13 Exchange Bag

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## Surprise! Puzzles

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.

**Tags:**
Exchange Gift, G4G13

## 4 x 13

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,…

**Tags:**
Exchange Gift, G4G13

## Type 14 Tessellating Pentagon

This item for the Gift Exchange is a 3D printed baker's dozen of irregular pentagons that tessellate the plane.

**Tags:**
Exchange Gift, G4G13

## Lights & Spheres

A 7cm green plastic sphere with a surface of conical projections, otherwise known as a Cando Massage Ball.

Titanium LED keychain flashlights: I will ship 200 with white LED, 100 with red, blue and green LEDs. Each attendee will receive one light…

Titanium LED keychain flashlights: I will ship 200 with white LED, 100 with red, blue and green LEDs. Each attendee will receive one light…

**Tags:**
Exchange Gift, G4G13, green plastic spiky ball, key chain, LEDs

## Cavalieri Content Cups

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…

## The Icosian Game

A game created by Sir William Rowan Hamilton. A traveler must visit 20 cities without revisiting any of them.

**Tags:**
dodecahedron, G4G13, Game, Puzzle

## Spiram Siderum

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

**Tags:**
Art, G4G13, magnetism, PhysicsFun