A) How many three digit numbers from $1, 2, 3, 4, 5, 6, 7, 8, 9$ can be created?
I answered this by $9 \times 8 \times 7 = 504$. The possible answers are 84 - 450 - 504 - 729
B) How many of those numbers are odd?
Possible answers are 42 - 405 - 280 - 225
I tried answering this with $9 \times 8 \times 5$ (since it should end with an odd number and there are $5$ of those in the offered numbers). However, it is not correct.
EDIT: I forgot to add that every number can only occur once.
Suggestions? Thank you in advance!
If every number can be used once , you must select first the unit cipher and you have $5$ choices, then you have only $8$ choices and then $7$, so the answer is:
$$5\times 8 \times 7=280$$
:)