Question

Consider a political discussion group consists of five democrats and six republicans. Four people are selected (at random) to attend a conference. In how many ways can four republicans be selected from the group?

Answer 1

Total number of republicans N=6

n= 4

Number of ways $= \frac{N!}{n!(N-n)!}$

$= \frac{6!}{4!(6-4)!} = \frac{5 \times 6}{2}= 15$