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Question
How many three-digit odd numbers are there?
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Solution
Available digits for filling any place = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0}
Since the hundred's place cannot be zero, the number of ways of filling the thousand's place is 9.
Number of ways of filling the ten's place = 10
Number of ways of filling the unit's place = 5 {1, 3, 5, 7, 9}
Total 3-digit odd numbers = 9\[\times\]10\[\times\]5 = 450
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