Addition Compensation
Introduction, Stage 4 – Mental Math – Single-Digit Add & Sub
Compensation is a powerful tool for making mental math easier. When adding two numbers, you can get the same sum by shifting over part of one number to the other. Adding 8 or 9 is easy using compensation. For example, add 6 + 9 by shifting 1 from the 6 to the 9, which gives 5 + 10. Similarly, 4 + 8 becomes 2 + 10.
Use compensation from twins and near twins to make all of the remaining math facts easier: 3 + 5, 3 + 6, 4 + 7, and 5 + 7. For example, using compensation, 5 + 7 is the same as 6 + 6.
More than one way: Some math facts can be done several ways. Challenge your child to find more than one way to do a problem. For example, 5 + 7 can become 6 + 6, but it can also become 2 + 10. This kind of math play will lead to lasting insights.