Question

There are 20 students in a 5th grade class. Four of these students will be selected to be patrols. In how many ways can the four patrols be selected?

Answer 1

4845 ways

Explanation:

We need to form groups of four students among the total of 20 students, and the order of the students inside the group does not matter, so we have a combination problem.

To solve this problem, we just need to find the combination of 20 choose 4:

C(20, 4) = 20! / (16! * 4!) = 20 * 19 * 18 * 17 / (4 * 3 * 2) = 4845

There are 4845 ways of selecting this group of four patrols.