thank you for your answer giddi77!
I can understand your reasoning except from this part:
"Words with 2 letetrs repeated:
2Rs: 2R's,1F or 2R's,1T = 3*2 =6
Similarly for 2Fs = 6 "
You covered 2Rs and 2Fs but where are the 2Ts ?
Oops! I somehow assumed that there is only 1 T:
Infact for the 2T's there will be 6 more combinations:
2T's,1F or 2T's,1R
2T's,1F = 3!/2! (3 combinations in where 2 letters are repeated) = 3
2T's,1R = 3!/2! = 3
So final answer = 1 + 6 + 6*3 = 25!
What you are missing in your list are single letter combinations:
So the total would be 25! HTH.
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