3780
If you consider every letter in the word "tennessee" to be unique there is 9!, or 362880 different ways to arrange the letters. So let's use that as a starting point.
Now there's 4 e's, which we really don't care how they're arranged. So divide by 4!, or 24. Giving us 362880/24 = 15120 different ways to arrange the letters.
There's also 2 n's. So divide by 2!, giving us 15120/2 = 7560 different ways.
Don't forget the s's either. So another division by 2!, giving 7560/2 = 3780 different ways.
And there's no more duplicate letters, so the final figure is 3780 different ways to arrange the letters in the word "tennessee".
