Unit 3 · Counting

Chapter 3.1

Multiply or Add?

Most counting mistakes are not arithmetic errors: they multiply where they should add, or add where they should multiply.

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By the end

  1. 01Multiply when choices happen in sequence, add when cases are separate
  2. 02Split a count into cases that neither overlap nor leave anything out
  3. 03Fill the most constrained position first

In unit 3

  1. 3.1Multiply or Add?
  2. 3.2Count What You Don't Want
  3. 3.3Arrangements and Overcounting
  4. 3.4Choosing, Pascal, and Stars and Bars
  5. 3.5Counting Two Ways
  6. 3.6Too Few Boxes
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