Question

How many different 9-letter words (real or imaginary) can be formed from the letters in the word assistant?

Answer 1

There are 9! ways in total, however, notice that certain letters repeat themselves. 

For example, a permutation could be assistant but the third s could replace the first it would still be assistant. 

So, 

9!/(3!)(2!)(2!) <-- 3 s's, 2 a's and 2 t's 

Therefore, the total permutations are: 15120

Hope I helped :)