Nancy Anderson, EdD
Mathematics Teacher ~ Author ~ Consultant
Math Ed FAQs
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.
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