Permutations with restrictions

Question

A security code consists of 3 letters selected from A, B, C, D, E, F followed by 2 digits selected from 5, 6, 7, 8, 9. Find the number of possible security codes if no letter or number can be repeated.

Answer 1

nPr = n!/(n-r)!

6P3 x 5P2

=6!/(6-3)! x 5!/(5-2)!

=6!/3! x 5!/3!

=6x5x4 x5x4

=30x80

=2400