How many 3-digit odd numbers exist, with no repetition? Ex: 871 counts, but 777 does not.
Question
How many 3-digit odd numbers exist, with no repetition? Ex: 871 counts, but 777 does not.
Solution
Sure, let's break it down:
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A 3-digit number has three places: hundreds, tens, and units.
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Since the number is odd, the unit place can be filled by any of the 5 odd numbers from 0 to 9, which are 1, 3, 5, 7, and 9.
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The hundreds place can be filled by any of the remaining 9 digits (0 can't be used because it's a 3-digit number).
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Finally, the tens place can be filled by any of the remaining 8 digits.
So, the total number of 3-digit odd numbers with no repetition is 5 (choices for the units place) * 9 (choices for the hundreds place) * 8 (choices for the tens place) = 360.
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