Combinatorics › Permutations and arrangements › Arrangements of letters
Passwords with equal lowercase counts
High school · ●●○○○ 20 pts
Computer passwords are between 6 and 8 characters long. Each character is an upper case letter, a lower case letter or a digit. Each password has at least one upper case letter, at least one lower case letter and at most one digit. Let be a set of such passwords. What is the minimum size of that guarantees at least two passwords in have the same number of lower case letters?