How many 3-letter words can we make from the letters A, B, C, and D, if we are allowed to repeat letters, and we must use the letter A at least once?
A B C = 3! = 6
A B D = 3! = 6
A C D = 3! = 6
A B B = 3! / 2! = 3
A C C = 3! / 2! = 3
A D D = 3! / 2! = 3
A A B = 3
A A C = 3
A A D = 3
A A A = 1
So....I get 37
Anyone get something different ???
+1206 
