By Mary Jane Sterling

Part of 1,001 Pre-Calculus Practice Problems For Dummies Cheat Sheet

Counting the number of ways to perform a task is fairly simple — until the number of choices gets too large. Here are three counting techniques used in pre-calculus:

  • Permutations: How many ways you can choose r things from a total of n things when the order of your choices matters

  • Combinations: How many ways you can choose r things from a total of n things when the order of your choices doesn’t matter

  • Multiplication principle: How many different possibilities exist if you choose 1 from a things, 1 from b things, 1 from c things, 1 from d things, and so on.

Use the following formulas for these counting techniques:

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