Which basic facts can efficiently be solved by these subtraction strategies?

Edward C. Rathmell
University of Northern Iowa

The zero generalizations allow students to quickly solve 19 of the basic subtraction facts. Subtracting 0 or subtracting a number from itself become easy.

Counting back can be used to quickly solve problems where you are subtracting 1 or 2. This includes 18 additional problems.

Counting up can be used to quickly solve problems where there is a difference of 1 or 2. This includes 14 additional problems. Together, the generalizations, together with counting back and counting up, provide students an efficient way to solve 51 of the basic subtraction facts.

Using doubles can provide a quick way to solve another 19 basic facts. In each of these cases, doubling the part is no more than a difference of one from the whole.

Using ten as a bridge or stepping stone can help students quickly subtract 8 or 9. Facts, with a difference of 8 or 9, can also be solved by using ten. This enables students to quickly subtract another 18 basic facts. Collectively, these strategies help children easily solve 88 of the 100 basic subtraction facts.

All other facts can all be efficiently solved by using know addition facts. In fact, as soon as students know addition facts and understand the part-part-whole relationship, they are able to solve subtraction by using what they already know about addition.

Return to Questions