Your class is holding elections to choose a leadership committee of 4 students. If there are 30 students in the class, how many different leadership committees would it be possible to elect?

810,000

27,405

120

657,720

Since order is not important we are only looking for unique combinations of 3, so we need to use the "n choose k" formula.

n! / (k! (n-k) !), n=number of elements to choose from, k is the number of choices made ... in this case:

30! / (4! (30-4) !)

30! / (4!*26!)

27405