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Home > A2C > Chapter 10 > Lesson 10.2.5 > Problem 10-125


Andrea has just purchased a five-digit combination lock. It 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.

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

    There are no repeats, but order does matter.

    10P5 = 30,240

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

    Now she has ten choices for each digit.