This is a wonderful game with many variations and lots of underlying mathematical ideas. It can be played cooperatively or competitively - or both, by working together in teams to compete with other teams. Children often master the rules more quickly than do adults, which adds to their fun. Here’s a brief outline of the way I introduce the game to people from about 8 years old to 80. If you would prefer a much more detailed approach, with many examples, go to page 30 of the Nov 2016 issue of The Variable .

Digital pictures Have you ever wondered how computers and all things digital handle pictures? This simplified version can be turned into an open-ended game. Error Detection Free your inner mathemagician! Mystify your audience! Give them lots of time to try to figure out what you are doing – you may be surprised by which student does figure it out. This game is based on one method that computers check whether transmitted information might have errors.

Geometry is a huge part of mathematics, although it often gets passed over in the school curriculum. Here are some great games and puzzles that help build geometric intuition. Some support more formal mathematical study as well. Pentominoes Make two and three dimensional shapes from drinking straws. The three-dimensional shapes are particularly eye-catching. (Small hands will require some help with those.) You can also create towers using the straws - the most stable are built from triangles.

15-Scratch and 24-Scratch are great games for almost anywhere you have a few spare minutes. You don’t need anything at all to play them, but it helps if you have something to write on and something to write with. A more complicated version allows more operations and can entertain people for hours. If you write the numbers from 1 to 100 on a board with space beside each one, students can put up their solutions over several days.