Answer:
120 different words
Explanation:
The max longest word has 4 letters
So the word can consist of 1 letter. The number of such wordds is 3 (A,O or M)
The word can consist also of 2 letters ( letters can be repeated in the word-
the word like AA or MM are possible). The number of such words is 3*3=9
The word can consist also of 3 letters ( letters can be repeated in the word-
the word like AMA or MMM are possible). The number of such words is 3*3*3=27
The word can consist also of 4 letters ( letters can be repeated in the word-
the word like AAAA or MAOM are possible). The number of such words is 3*3*3*3=81
So total number of words is 3+9+27+81=120