First graders are building their numbers sense and working on computation skills as they learn about addition and subtraction strategies. Thus far we have learned about zero facts, counting on, and counting back.
The zero facts strategy simply means that any number plus or minus zero equals that number. We have applied this strategy to simple single digit number sentences (0+7=7) up to three and four digit number sentences (324+0=324).
Counting on and counting back are strategies to use any time you are adding or subtracting 1, 2, or 3. We have found that no matter how big the number, counting on or back 1, 2, or 3 is fast. The key is to always start with the biggest number. Once again we will apply this strategy to single digit number sentences (3+6=9, 8-2=6) and multi-digit number sentences (29+2=31, 391-3=388).