Unit 3 · Counting

Chapter 3.2

Count What You Don't Want

Sometimes the things you want are hard to count, but the things you don't want are easy.

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By the end

  1. 01Count the complement when 'at least' or 'not' makes the direct count messy
  2. 02Correct for overlapping groups with inclusion-exclusion on two or three sets

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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