Papys Mini-Calculator.
The method we have used to introduce children to mechanical and mental arithmetic employs the distinct advantages of the binary system over other positional systems, while at the same time taking account of the decimal environment in which we are immersed.
Inspired by some work of Lemaitre, this variety of two-dimensional abacus uses the binary system on boards which are arranged according to the decimal system.
The colours recall the red family of the set of Cuisenaire rods and help to make the four rules of the machine easily accessible.