Answer: 5040
Step-by-step explanation:
Given : Number of choices to make a four digit code ( 0 to 9)= 10
If repetition is not allowed , then we use Permutations to find the number of different code groups can be designed.
The number of permutations of n things , taking r at a time is given by :-
Then, the number of permutations of 10 numbers , taking 4 at a time is given by :-
Hence, the number of different code groups can be designed= 5040