Pre-Calculus: 1001 Practice Problems For Dummies (+ Free Online Practice)
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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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About This Article

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About the book author:

Mary Jane Sterling is the author of numerous For Dummies books. She has been teaching at Bradley University in Peoria, Illinois, for more than 25 years.

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