How can we teach using addition facts for subtraction?

Edward C. Rathmell
University of Northern Iowa

This strategy works efficiently for all subtraction facts. It helps children connect addition and subtraction ideas in a way that enables them to answer questions about either addition or subtraction if they know the answer to the other.

By informally using the part-part-whole language over an extended period of time, children will learn that known addition facts can be used to help students solve subtraction problems. Knowing the parts and the whole informs us about all of the addition and subtraction problems in the number family.

As described above in the other subtraction strategies, hiding the set that is left after subtracting encourages students to think in a way other than counting what is left. The strategies that evolve from these situations lead to using addition to help. The hidden set encourages students to use addition. The ten frame and the number line can be used to confirm that thinking and help children make sense of it.

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