# How many words can be formed by taking four letters at a time out of the letters of the word MATHEMATICS? [duplicate]

The question is:

How many words can be formed by taking four letters at a time out of the letters of the word MATHEMATICS?

I know how to do it for non-repeating letters. You simply permute $$4$$ things taken from $$11$$ at a time. But how do I do this? How to subtract out the words that have repeated letters in them? What should I divide the total permutations with?