Question

40 letter codes an identification code is to consist of three letters followed by four digits. How many different codes are possible if The first letter must be an A,B,C, or D and the repetition is not permitted

Answer 1

Since the letters cannot be repeated in the same order, you have a permutation. If the numbers cannot be repeated either then you have another permutation.

Then the number of codes would be P1 + P2.

Answer 2

thanks for your help