## Thinking Mathematically (6th Edition)

Combination problems involve: $\bullet$Selections of r items from a set of n items, $\bullet$Where any item can be chosen only once and $\bullet$Where the order of the selections is unimportant. Sample: "In how many ways can a three-member committee be formed from a group of seven students?" (Selecting r=3 out of n=7 students ... in ${}_{7}C_{3}$ ways)