Half Area Quadrilateral

Half Area Quadrilateral

Make three equally spaced notches along the four sides of a square. Choose one of these three notches on each side. Connect them up to form a simple quadrilateral. For example, here we have chosen the middle notch on each side. What is the area of this...
Babylonian Spiral

Babylonian Spiral

Start by drawing a point on a cartesian grid. The position of the point has been selected carefully. The student at the back right of the class begins. They know nothing. They may either take a guess at what will happen next – or may ask for the next slide....
Arrows

Arrows

Arrows (Eggleton & Fraenkel, 1975) Categorize 9 games based on the answer to two questions: 1) Will Emperor Jiaqing win / tie / lose if he goes the first. 2) Will the Pirate, Ching Shih, win / tie / lose if she goes the first. The games are all variants of the...
Ruffian Ritual

Ruffian Ritual

Ruffian Ritual Not everyone is nice. Not everyone even pretends to be nice, but their is still honour and protocol among thieves.  Let's say that you're spying on a den of thieves and ruffians. The first thing you notice when they get together is that they all...
Kobon Triangles

Kobon Triangles

Kobon Triangles (Kobon Fujimura, 1981) Math Puzzles do not get more beautiful than this one from Japan.  It should be used by either elementary instructors who need to give their students practice holding a ruler and drawing a straight line or by junior high...