by tommywallach Fri Aug 01, 2014 10:32 pm
Hey Baily,
This is a combinatorics question, so we would use the slots method:
_ _ _
Three slots for the three digits.
8 _ _
Eight choices for the first slot (because it can't be 5, and it can't be 0, because a three-digit number can't start with a 0).
8 9 _
Nine choices for the second slot, because we can choose any number except 5.
8 9 4
Only four choices for the third slot, because it can't end in 5, but it must be odd, meaning it must end in 1, 3, 7, or 9.
8 * 9 * 4 = 288
-t