Question 1133836
How many odd numbers of at most three digits can be formed using the digits 0,1,2,3,4,5 without repetitions? 
It says the answer is 63.
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The units digit has to be 1, 3 or 5 to be odd, that's 1 of 3
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Assuming leading zeroes are not allowed, eg, 025, (tho it should be specified, we should not have to make assumptions), the 100's digit for 3 digit numbers must be 1,2,3,4,or 5, but one of the odd numbers is used, so it's 1 of 4 for the 100's digit.
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That's 3*4 = 12 possible 3 digit odd numbers.
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There are 3 possible 1 digit numbers, 1, 3 & 5
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For 2 digit numbers:
The units is 1 of 3.
The tens digit is 1 of 6
3*6 = 48
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48 + 12 + 3 = 63