Question

How many subsets of five elements each can be made from a set of seven elements?

42
21
14

Answer 1

When creating a subset of 5 elements from 7 elements, order should not matter. Therefore, we use the combination formula over the permutation formula. The combination formula given n elements total and r elements used is n! / [r!*(n-r)!]. Substituting 7 for n and 5 for r, we get: 7! / (5!*2!) = 7*6 / 2 = 21 21 subsets can be created