How many combinations with 4 letters?
256 iThink
* * * * *
It depends on combinations of how many. There is
1 combination of 4 letters out of 4,
4 combinations of 3 letters out of 4,
6 combinations of 2 letters out of 4,
4 combinations of 1 letter out of 4.
Than makes 15 (= 24-1) in all. Well below the 256 suggested by
the previous answer.