Addition and       Subtraction Facts       to 20   Introducing the Concept   Developing the Concept

## Addition and Subtraction Facts to 20

• Why should I learn the facts?
Help children to volunteer answers, such as they will need to know the facts to add the score for games, to know how much to pay for two or more items, to make change, to find how many when two or more groups are combined, to find how many are left, how many more, how many fewer, and so on. You can also tell children that these facts are important to learn because they will need them later as they do more complex math.

• If I learn one fact, will it help me to remember other facts?
Explain to children that once they learn a fact, they know the fact family. They can use doubles facts to find the answer for a doubles plus one fact. Also explain that strategies such as the following can help them remember facts: Zero doesn't change a number; one makes a number go up or down by 1; when adding a number to 10, replace the zero in 10 with the digit being added; and when adding 7, 8, and 9 to another number, break apart that number to make a 10 and then add the remaining number.

• If I don't know a fact, what can I do?
Remind children that they can try to remember a related fact or use one of the strategies they learned to figure out the answer.