Counting the Number of Subsets in a Set

Problem: How many groups can be formed from 5 persons?

The Power Rangers

First, we represent the persons by small letters a, b, c, d, and e, and we denote a group whose members are c and d as {c, d}. We can have a group with 2 members, 3 members, 4 members, and 5 members.  The members in each group are listed below.  » Read more