Tina has to create a password for the security of a software program file. She wants to use a password with 3 letters. How many passwords are allowed if no letters are repeated and the password is not case sensitive?

Question

anonymous · Answer

she has 26 options for letter 1, 25 for letter 2 and 24 for letter 3, so she has 26*25*24 = 15600 options

anonymous · Answer

Well, there are 26 letters, case sensitivity doesn't matter. If it DID matter, then we would have 52 letters. The total permutation would be one of:
$$P(n, k) = n! / (n-k)!$$
Where 'n' is 26 and k is 3.