Chapter 12 - Data Analysis and Probability - 12-6 Permutations and Combinations - Practice and Problem-Solving Exercises - Page 754: 19

42

Use the formula of permutation: $_{n}$P$_{r}$=$\frac{n!}{(n-r)!}$. Plug in 7 for N and 2 for R: $_{n}$P$_{r}$=$\frac{n!}{(n-r)!}$ $_{7}$P$_{2}$=$\frac{7!}{(7-2)!}$ -simplify- $_{7}$P$_{2}$=$\frac{7!}{5!}$ -write using factorial- $_{7}$P$_{2}$=$\frac{7*6*5*4*3*2*1}{5*4*3*2*1}$ -simplify- $_{7}$P$_{2}$=42