How many of these four digit numbers are odd/even? For the following question: 

How many four-digit numbers can you form with the digits $1,2,3,4,5,6$ and $7$ if no digit is repeated?

So, I did $P(7,4) = 840$ which is correct but then the question asks, how many of those numbers are odd and how many of them are even. The answer for odd is $480$ and even is $360$ but I have no clue as to how they arrived to that answer. Can someone please explain the process?
Thanks!

Multiply the answer by $\frac{4}{7}$ since there are 4 odd numbers and $\frac{3}{7}$.
