Nancy Anderson, EdD

Mathematics Teacher ~ Author ~ Consultant

​The Big Ideas

  • There are three models of addition: join, compare, part-whole:
    • ​Join: Each addend is its own set; the sum is the total of both sets
    • Compare: The first addend is the size of one set and the 2nd addend expresses the amount we add to that set to get the size of another set 
    • Part-part-whole: Each addend is part of one set; the total is the size of the whole set
  • Students can think of any subtraction as an "addend unknown" addition fact
  • Knowing about the commutative property and putting that property to work can cut students' work in half
  • Students can develop fluency by working on subsets of facts at a time. They should progress through the facts by using known facts to derive unknown sums.