Games for Educators

Before starting these subtraction activities, practice any of the following skills that happen to be weak for your child:

• Add and subtract 0, 1, 2 (and perhaps 3)
• Subtract numbers 1 or 2 apart
• Know the number bonds for 10 – they make subtracting from 10 easy (e.g. 3 + 7 = 10-> 10- 7 = 3)
•  Subtract 10 from numbers from 11 to 19 (e.g. 14- 10 = 4)

For problems with numbers larger than 10, such as 13 – 8, break them into two differences. The distance from 13 to 8 is the distance from 13 to 10 plus the distance from 10 to 8. Writing this out with numbers, 13 – 8 becomes (13 – 10) + (10 – 8) = 3 + 2 = 5.

This simplifies the mental load considerably by breaking these subtractions into two manageable parts. Subtracting 10 from a number between 10 and 20 is very straightforward. Learning how to subtract numbers from 10 is a matter of learning the number bonds for 10.

Compensation for subtraction means adding or subtracting the same amount to both numbers to maintain the distance between them. For example, 12– 8 = 13– 9 = 14– 10.

Use compensation on 13– 8 by adding 2 to both numbers to turn the problem into 15– 10. Notice how much easier the problem became using this minor adjustment!

Single-digit problems can also be done this way. For example, 3 can be added to both numbers in 7– 3 to make it 10 – 6 = 4.