Thread: probability problem

I cant remember how to solve these.

A computer password consists of eight letters. How many passwords are possible? Assume there is no difference between lower-case and upper-case letters.

Please help!

Originally Posted by sevenlovesyou

I cant remember how to solve these.

A computer password consists of eight letters. How many passwords are possible? Assume there is no difference between lower-case and upper-case letters.

Please help!

What we are dealing with here is a permutation.

Recall that where .

Since the password can contain only letters, and we are to assume that there is no difference between lower and upper case we must let [if there was a difference between upper and lower case, ]. Since the password can only be 8 letters long, let .

So we see that we now have

Can you take it from here?

--Chris

It has been my experience that passwords allow for repetitions, such as “youuttta”.
In that case the answer would be .