Unfair dice

This is a model of an unfair dice. Depending on the model you choose, the dice has a hole beneath one (or more if you want) of its faces. This means that the face above this hole is more likely to come.

I use this in classrooms to introduce the idea of probability (law of large numbers). As a motivation, I ask the students to give which face is more likely to come up. Then I can check their predictions by throwing the dice in a cup of water (because of buoyancy and viscosity, the side with the hole will with nearly 100% of the time come up). Sometimes I add a couple of fair dices to make things more challenging. Note however that I found it hard to print a fair dice (but it might be due to my printer's poor accuracy). Defects in the geometry (e.g. the print direction or an uneven bed) have a big influence.

The hole is so designed that it can be printed in the upward/downward direction too (there is an inbuilt support in the design). This setting was important for me as I realised