Chapter 12 - Data Analysis and Probability - 12-6 Permutations and Combinations - Practice and Problem-Solving Exercises - Page 754: 23

90

Use the formula of permutation: $_{n}$P$_{r}$=$\frac{n!}{(n-r)!}$. Plug in 10 for N and 2 for R: $_{n}$P$_{r}$=$\frac{n!}{(n-r)!}$ $_{10}$P$_{2}$=$\frac{10!}{(10-2)!}$ -simplify- $_{10}$P$_{2}$=$\frac{10!}{8!}$ -write using factorial- $_{10}$P$_{2}$=$\frac{10*9*8*7*6*5*4*3*2*1}{8*7*6*5*4*3*2*1}$ -simplify- $_{10}$P$_{2}$=90