Chapter 11 - Counting Methods and Probability Theory - 11.3 Combinations - Exercise Set 11.3 - Page 707: 15

4060

The number of possible combinations if r items are taken from n items is nCr = $\frac{n!}{r!(n-r)!}$ 30C3 = $\frac{30!}{3!(30-3)!}$ $\\$ =$\frac{30!}{3!27!}$ $\\$ =$\frac{30*29*28*27!}{3!27!}$ $\\$ =$\frac{30*29*28}{3*2*1}$ = 4060