STRIP BOARD (including doubles)
g. Doubles of Numbers
Materials: addition strip board and strips
Control Chart 1
We find the doubles of numbers by taking a blue strip: 1 and the same second addend; the pink strip for 1. The strips are placed on the board, and the combination is written on the paper. The sum is read at the top. The one strips are returned to their places, and the twos are added, etc.
N.B. Here the teacher helps the child reflect on his work, thus noticing that not only is 9+9=18, but also that 1/2 of 18 = 9. The possibility for dialogue here is very great and is a way of engaging langugae in the course of understanding mathematics.
Control of error: Control Chart II on which the double of each number is found at the top of each column.