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 ✎
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, 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?