Joe wants to find all the four-letter words that begin and end with the same letter. How many combinations of letters must he examine? A word is any sequence of letters, such as MTHM, and does not have to be English.
There are 26 letters to choose from for the first letter; 26 for the second letter; 26 for the third letter; and 1 for the last letter (it must be the same as the first letter). This gives us
