Question

How many different license plate number can be made using 2 letters followed by 4 digits selected from the digits 0-9

a) if letters and digits may be repeated?
b) if letters may be repeated, but digits may not be repeated?
c) if neither letters nor digits may re repeated?

Answer 1

it was suppose to say pre cal sorry

Answer 2

letters: usually do not use O.
Let N be number of letters, ten the number of numerals.

a) N*N*10^4
b) N*N*10!/(10-4)!
c) N!/(N-2)! * 10!/(10-4)!