I am struggling with a problem from my text book, and was wondering if I am on the right path. I know I need to combine the amount of length $1$ strings all the way to length $5$ strings. I just do not know if I am doing it right.
What I have is $\binom{26}{5}+\binom{26}{4}+\binom{26}{3}+\binom{26}{2}+\binom{26}{1}.$
I am sorry to just ask a am I on the right path question, but I am stuck and this concept is important through the rest of the chapter.
Thank you for the help!
Order is important when counting strings, and you must also consider repetition. If we have an alphabet with two letters $a$ and $b$ then the amount of strings of length two is $4=2^2$, namely $aa$, $ab$, $ba$ and $bb$. However $\binom{2}{2}=1$.