Note.....choosing an "a" first......we could pair this with 25 other letters in alphabetical order
Or...if we chose "b" first, we would have 24 other choices in alphabetical order
Or...choosing "c" first gives us 23 other choices in aplabetical order....so we have
25 + 24 + 23 + ....+ 3 + 2 + 1 = the sum of the first 25 positive integers =
(25)(26)/ 2 = 325 "words" in alphabetical order
We could also see this in another way.....we could take the permute of P(26,2) = 650 different "words" in any order....but ....only 1/2 of these would be any good, because the other half would not be in alphabtical order [the order would be reversed] ....so ....650 * 1/2 = 325
