Problem: What is:9! over 2!3!4!
9!
--------
2!3!4!
9*8*7*6*5*4*3*2*1
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2*1 * 3*2*1 * 4*3*2*1
We can remove all the ones; they don't change the value.
9*8*7*6*5*4*3*2
------------------------
2 * 3*2 * 4*3*2
9 / (3 * 3) = 1, so remove those numbers.
8*7*6*5*4*3*2
-------------------
2 * 2 * 4*2
4/4 = 1, so remove those.
8*7*6*5*3*2
-----------------
2 * 2 * 2
8/(2*2*2) = 1, so remove those.
7*6*5*3*2
--------------
1
Multiply what's left.
7*6*5*3*2 = 1260