Exercise 2 - Page 123

2. In how many ways can we choose five people from a group of ten to form a committee?

The order we choose people here does not matter. Therefore we have a combination, as long as there are 5 people choosen to form a committee.

\({10\choose 5} = \frac{10!}{5!(10-5)!} = \frac{10!}{5!5!}\)

so \({10\choose 5} = \frac{10*9*8*7*6}{5*4*3*2*1} = \frac{30240}{120}\)

Therefore: \({10\choose 5} = 252\)

So there are 252 ways to choose 5 people from 10 to form a committee.