## Geometry: Common Core (15th Edition)

Order does matter, so we must use a permutation. We know that: $_nP_r = \frac{n!}{(n-r)!}$ $_9P_5 = \frac{9!}{(9-5)!}$ $\frac{9!}{4!}$ We also know that: $x! = x(x-1)(x-2)...(1)$ Thus, we have: 15120