Ways to Make 10

Making 10 is the single most important computational strategy in early arithmetic. A student who knows all the ways to make 10 and who can use that knowledge to simplify additions has a permanent mental math advantage. 8+5 becomes 10+3 because 8 needs 2 to make 10, and taking 2 from the 5 leaves 3. This strategy eliminates almost all counting-on-fingers dependency for sums to 20.