Thinking Mathematically (6th Edition)

The number of possible combinations if r items are taken from n items is nCr =$\frac{n!}{r!(n-r)!}$ We find the number of ways that a female professor can be chosen when there are four female professors. = 4C3 x 1! =$\frac{4!}{(4-3)!3!}$ =$\frac{4*3!}{3!1!}$ =$\frac{4}{1}$ = 4 ways