Hello,
4 different letters and 3 different digits
X represent a letter
- represent a digit
All letters must be kept together:
4 possiblities
XXXX---
-XXXX--
--XXXX-
---XXXX
There are 26 letters.
For each possiblity:
26 choices for the 1 letter
25 choices for the 2 letter
24 choices for the 3 letter
23 choices for the 4 letter
There are 10 digits:
10 choices for the 1 digit
9 choices for the 2 digit
8 choices for the 3 digit
Numbers of codes: 4*26*25*24*23*10*9*8=1033344000.