Joe wants to find all the four-letter words that begin and end with different letters. How many combinations of letters satisfy this property?
Here's what I think:
Twenty six choices for the first letter ....this leaves only 25 choices for the last letter for each first letter choice.
the second and third letters have 26 letter choices
26 x 26 x 26 x 25 = ............ four letter 'words' (most are non-sensical and may contain no vowels etc)