We can count books, tables, and houses and say that we have counted so many things but we do not add books, tables, and houses. We add books and books, tables and tables, houses and houses.
We count by ones. When we add three beads and two beads we are counting by ones, for it means that we are adding three ones of beads and two ones of beads, making five beads in all.
From 1 to 9 we use only one figure to tell how many we mean. When we wish to say in writing that we have ten of anything we write a 0 after the 1 and have 10, ten.
1. Add 1 to every number up to 10; later to 20.
2. Subtract 1 from every number up to 10; later to 20.
3. Add:
+2 +3 +4 +5 +6 +7 +8 +9 +10
+2 +3 +4 +5 +6 +7 +8 +9 +10
Here the addends are equal and easily added. The figures should be placed as above and not 2 + 2, 3 + 3, etc., because the vertical form is the natural one which the child will use all through life. It does not look so formal and represents better what he really does with the objects.
4. Add:
+1 +2 +3 +4 +5 +6 +7 +8 +19
+2 +3 +4 +5 +6 +7 +8 +9 +10