### Home > CCA2 > Chapter 10 > Lesson 10.1.1 > Problem 10-21

10-21.

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. For help with this problem, refer to the Math Notes box in this lesson. Homework Help ✎

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

How many five-digit combinations are possible if she

*can*repeat the digits?

There are no repeats, but order does matter.

_{10}*P*_{5} = 30,240

Now she has ten choices for each digit.