This unit includes the properties of addition and multiplication, negative numbers and fractions.

  1. CME’s Addition and Multiplication Table Patterns
  2. David Cox uses properties to justify steps
  3. James Tanton uses area as a model for multiplication, and uses the model to explain why a negative times a negative is a positive.
  4. A good problem, originating with PCMI, for adding and subtracting fractions.
  5. Alternate division algorithms for fractions, via Chris Danielson. Why do they work?

Here’s everything posted under “Arithmetic,” including stuff that didn’t make the cut.

Still looking for:

  • A really good way to handle multiplication and division of fractions.

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