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Question
How many different five-digit number licence plates can be made if
the first-digit cannot be zero, but the repetition of digits is allowed?
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Solution
Since the first digit cannot be zero, the number of ways of filling the first digit = 9
Number of ways of filling the second digit = 10 (Since repetition is allowed)
Number of ways of filling the third digit = 10
Number of ways of filling the fourth digit = 10
Number of ways of filling the fifth digit = 10
Total number of licence plates that can be made = 9\[\times\]10\[\times\]10\[\times\]10\[\times\]10 = 90000
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