Joe wants to find all the four-letter words that begin and end with the same letter. How many combinations of letters satisfy this property?
There is \(26\) ways to choose the first/last numbers. Then, there are \(26\) ways to find the second and third letter. Finally, there is \(1 \) way to choose the last number. Multiplying all these numbers, we get \(17576\) combinations of letters.