PROBABILITY

Now if you could tell the B's apart and the I's apart

like you can when you color the two B's and the two I's 
different colors, like this:

PROBABILITY

then the number of ways would be 11!  However when the like letters
are colored the same, then, for example, you can't tell the following 4 arrangements apart: 

1. LBIRTIOBYPA
2. LBIRTIOBYPA
3. LBIRTIOBYPA
4. LBIRTIOBYPA

because they will all look the same, like this

   LBIRTIOBYPA

So we must divide the by 4.

The reason we divide by 4 is because there are 2! ways to arrange the
two B's TIMES 2! ways to arrange the two I's, and 2!*2!=2*2=4

So the answer is   

Edwin