Pile up paper cut-outs of triangles, squares, circles, hexagons, ovals. Sort them — by sides, by colour, by symmetry, by size. Different rules, different piles.
Sorting rules to try
- Number of sides — 3, 4, 5, 6, more, none
- Has straight sides vs has curves
- Has right angles vs doesn't
- Has symmetry vs doesn't
Get a friend to guess your sorting rule from the piles alone. If they can, your rule is clean. If they can't, refine it.