SOLUTION: 4 digit number license plates can be made if: first digit cannot be zero and repetition is not allowed.

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Question 1202125: 4 digit number license plates can be made if:
first digit cannot be zero and repetition is not allowed.

Answer by Shin123(626) About Me  (Show Source):
You can put this solution on YOUR website!
There are 9 choices for the first digit, since it can't be zero. For the second digit, you can't pick the same one as the first digit, so there are 9 choices. For the third digit, you can't pick the same one as the first or second digits, so there are 8 choices. For the last digit, you can't pick the same one as the first, second, or third digits, so there are 7 choices. In total, there are 9%2A9%2A8%2A7=4536 possible license plates.