Let's review...

How many ways can you arrange the letters in this word?

It's just like books -- 6 letters...

But, what if some letters are repeated?

What about this word?

The problem is that these letters are the same.  So, we can't tell the difference between these two arrangements:

and

which O is which O?

The answer is that it doesn't matter!

So, when we figure this guy out, we have to divide out that double "O" problem.

Check it out:

     To arrange 6 letters is 6!

     To arrange the two O's would be 2!
                                         

So, the number of ways to arrange the letters in

is