Chapter 11 - Counting Methods and Probability Theory - 11.3 Combinations - Exercise Set 11.3 - Page 707: 10

792

The number of possible combinations if r items are taken from n items is nCr = $\frac{n!}{r!(n-r)!}$ 12C5 = $\frac{12!}{5!(12-5)!}$ =$\frac{12!}{5!7!}$ =$\frac{12*11*10*9*8*7!}{5!7!}$ =$\frac{12*11*10*9*8}{5*4*3*2*1}$ = 792