using the digits 3, 4, 5, 6, 7, 8, and 9, how many 4-digit numbers can be constructed if the number must begin with an odd digit and digits may not be repeated?
We have four choices for the first digit
And the other digits can be permuted in P (6,3) ways .....so....
4 * P(6, 3) = 480 four digit numbers
