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Curiouspoet
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Counting Lists With Repetition
How many ways can you create an 8 letter password using A - Z where at most 1 letter repeats?
I'm not sure how to attack this problem but first I thought that A-Z considers 26 letters so with no restrictions on passwords we can create 268 passwords. I'm thinking it's 268 - X, where X is a term or a series of terms, but I'm not sure how to determine them, or if this is even the correct setup.
Well there are two cases given by the restrictions as follows:
A) No letter repeats in which we have a k list without repetition which is given by (n)k = n!/(n-k)!
B) One letter repeats in which case I think it's 26*[(n-1)!/(n-k-1)!].
And of course in this case n = 26 k = 8. Is this correct? If not could someone give me a hint?
Homework Statement
How many ways can you create an 8 letter password using A - Z where at most 1 letter repeats?
Homework Equations
The Attempt at a Solution
I'm not sure how to attack this problem but first I thought that A-Z considers 26 letters so with no restrictions on passwords we can create 268 passwords. I'm thinking it's 268 - X, where X is a term or a series of terms, but I'm not sure how to determine them, or if this is even the correct setup.
Well there are two cases given by the restrictions as follows:
A) No letter repeats in which we have a k list without repetition which is given by (n)k = n!/(n-k)!
B) One letter repeats in which case I think it's 26*[(n-1)!/(n-k-1)!].
And of course in this case n = 26 k = 8. Is this correct? If not could someone give me a hint?
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