## Geometry: Common Core (15th Edition)

This involves a combination since the order does not matter. We know that: $_nC_r =\frac{_nP_r}{r!} = \frac{n!}{(n-r)!r!}$ $_{16}C_4 = \frac{16!}{(16-4)!4!}$ $\frac{ 16!}{4!12!}$ We also know that: $x! = x(x-1)(x-2)...(1)$ Thus, we have: 5330