In This Unit of Study…

Students use and explain a variety of counting strategies, and they reason about the sums and differences of basic facts through sums of 20. After using one-to-one correspondence to count a set of items, students begin to find more efficient methods for counting. Students relate the concept of counting on to addition and of counting back to subtraction. The ability to add and subtract within 20 translates to being able to find the sum of 3 whole numbers. Students represent problems by using objects, drawings, and equations with a symbol for the unknown value in all positions, while understanding that the sum or difference can be on either side of the equal sign.

B.E.S.T. Benchmarks

  • MA.1.NSO.2.2 Add two whole numbers with sums from 0 to 20 and subtract using related facts with procedural reliability. (only within 10)

Overarching Key Concepts

  • Add and subtract within 20 using ‘count on and count back’ strategies.
  • Add within 20 using doubles near doubles.
  • Add and subtract within 20 using the ‘make a ten’ strategy.