In how many ways can a committee of 4 be chosen from a group of 9 people?

Since this is a combination not a permutation problem, (order does not matter) you should use the "n choose k" formula.

C=n!/(k!(n-k)!)  where C is the number of unique combinations, n equals the total number of possible choices and k equals the specific number of choices.  In this case:

C=9!/(4!(9-4)!)

C=9!/(4!5!)

C=362880/(24*120)

C=362880/2880

C=126

So there are 126 unique ways to pick 4 people from a group of 9 people.