Summary

These abc tiles are something that both primary / elementary and secondary / high school children can use to understand algebra. With three simple tiles algebra makes immediate sense, and they look good too.

Instructions

The three tiles are a square, a quarter circle, and the shape left when the quarter circle is cut from a square.

Their use in a maths lesson is described here:
http://pinkmathematics.blogspot.fr/2013/02/tak-tiles-are-something-that-primary.html

They are inspired by "tak-tiles", a set of tiles for explaining algebra which are not at present commercially available. They do however approach the topic from a different angle, building up shapes, rather than themselves being composite shapes.

Ideally, a set of a dozen or so of these tiles would allow students to explore how a, b and c combine.