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Home > CCA2 > Chapter 12 > Lesson 12.2.2 > Problem 12-113

  1. Andrea has just purchased a five-digit combination lock that allows her to set up her own combination. She can use the numbers 0 through 9 for her combination, and she must use five digits. Homework Help ✎

    1. How many five-digit combinations can she make so that no digit is repeated?

    2. How many five-digit combinations are possible if she can repeat the digits, but cannot use the same digit twice in a row?

Although the problem says 'combination' this is actually a permutation
because the order you enter the numbers in the combination lock matters.

Since this is a special case you can use a decision chart.
How many choices does she have for each position?