Chapter 12 - Data Analysis and Probability - 12-6 Permutations and Combinations - Practice and Problem-Solving Exercises - Page 754: 29

9

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