64 = 65 Mathemagical Proof

64 = 65 Mathemagical Proof

64 = 65 Mathemagical Proof (Martin Gardner) Get your older students to break apart a convincing mathemagical trick by linking it to the Fibonacci sequence and calculating the slopes of some line segments. Younger students derive a lot of pleasure by figuring out that...
Taxi Cab Squares (geometry)

Taxi Cab Squares (geometry)

 Taxi Cab Squares  (inspired by the Inscribed square problem of Otto Toeplitz, 1911) Give your students practice with Cartesian coordinates as they explore a new variant of a famous, unsolved problem of Otto Toeplitz (1911). This problem has a very wide spectrum of...
Complete the Quadrilateral

Complete the Quadrilateral

Complete the Quadrilateral (Don Steward, 2013) Try finding the largest and smallest rhombus, rectangle, trapezoids etc. so their vertices  include a special point and the other vertices lie on the lattice points of a grid. The first half of the video is quite easy,...
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....
No Three in a Line

No Three in a Line

  No three in a line puzzle (Henry Dudeney, 1917) This is a great idea to get your students thinking about patterns. Watch the video above first. There are some changes that improve the experience: 1) I now start the class by getting them to solve the 3×3...