6. How many 6-symbol computer passwords can be formed if the first two symbols are letters (either upper or lower case) and the rest of the symbols are digits? (Letters and digits may be repeated.) Solution Here either upper case or lower case letters can be used, i presume they are to be treated as distinct, so 52 symbols for letters are available, and the rest of four symbols are digits. so 52*52*10*10*10*10 =27,040,000.

1. 6. How many 6-symbol computer passwords can be formed if the first two symbols are letters
(either upper or lower case) and the rest of the symbols are digits? (Letters and digits may be
repeated.)
Solution
Here
either upper case or lower case letters can be used,
i presume they are to be treated as distinct, so 52 symbols for letters are available,
and the rest of four symbols are digits.
so
52*52*10*10*10*10 =27,040,000