If a leading zero is allowed...
The first digit can be 0-9, ten possibilities.
The second digit can be 0-9, ten possibilities.
The third digit can be 0-9, ten possibilities.
The fourth digit can be 3-9, 7 possibilities.
So there are 10x10x10x7 = 7000 such codes.
If repetition of digits isn't allowed, then no13-digit sequencescan be formed from only 5 digits.
64 if repetition is allowed.24 if repetition is not allowed.
64 if repetition is allowed, 6 otherwise.64 if repetition is allowed, 6 otherwise.64 if repetition is allowed, 6 otherwise.64 if repetition is allowed, 6 otherwise.
10^7 if the repetition of digits is allowed. 9*8*7*6*5*4*3 , if the repetition of digits is not allowed.
It is 10000.
If repetition of digits is allowed, then 56 can.If repetition of digits is not allowed, then only 18 can.
If repetition of digits isn't allowed, then no13-digit sequencescan be formed from only 5 digits.
64 if repetition is allowed.24 if repetition is not allowed.
24 three digit numbers if repetition of digits is not allowed. 4P3 = 24.If repetition of digits is allowed then we have:For 3 repetitions, 4 three digit numbers.For 2 repetitions, 36 three digit numbers.So we have a total of 64 three digit numbers if repetition of digits is allowed.
64 if repetition is allowed, 6 otherwise.64 if repetition is allowed, 6 otherwise.64 if repetition is allowed, 6 otherwise.64 if repetition is allowed, 6 otherwise.
5040
10^7 if the repetition of digits is allowed. 9*8*7*6*5*4*3 , if the repetition of digits is not allowed.
5 ^12
125
It is 10000.
0123456789
-123456787