Question

A code word is either a sequence of three letters followed by two digits or two letters
followed by three digits. (Unless otherwise indicated, letters will means letters cho-
sen from the usual 26-letter alphabet and digits are selected from f0; 1; 2; 3; : : : ; 8; 9g.
Also, unless it is stated that letters have to be dierent, you should assume repeats
are allowed. Likewise for digits.) How many dierent code words are possible?

Answer 1

Is it (26*26*10*10*10) + (26*26*26*10*10)

Answer 2

Yep, looks right.

Answer 3

Yeah you're correct