## Algebra 1: Common Core (15th Edition)

This question involves permutations. The number of books read is: $_{10}P_4$ We know that: $_nP_r = \frac{n!}{(n-r)!}$ $_{10}P_4= \frac{10!}{(10-4)!}$ $\frac{10!}{6!}$ We also know that: $x! = x(x-1)(x-2)...(1)$ Thus, we have: 5040