ADDITION CHARTS AND COMBINATION CARD EXERCISES
d. Passage from Chart IV to Chart V (the Simplified Tables)
…box of combination cards
…Control Chart I and V (which has only 17 sums on two diagonals: external is even, internal is odd)
The child fishes for a combination, reads it and writes it down on his paper, i.e. 4+6. The first finger is placed at 4 on the left-hand column and moved along to the end of the row. The other finger is placed at the second addend, 6 on the left hand column, and is also moved along to the end of the row. The two fingers are then moved toward each other along the diagonal one step each at a time. Where they meet we read the sum. The next combination is 3+9=___ to emphasize that each finger goes the same distance. Then 2+9=___ is used as an example. The two fingers must meet on the internal diagonal. Other examples are given.
To bring a new slant of interest to this activity, the teacher brings into focus that when both addends are even, the sum is even. When both addends are odd, the sum is even. When one addend is even and the other odd, the sum is odd.
Control of error: Control Chart I