How many elements must a set have if the number of proper subsets of the set 1/2 of the total number of subsets of the set?

A proper subset of a set A is a subset that is strictly contained in A and excludes at least one member of A. The empty set is also a proper subset of any nonempty set.

So there is only 1 element that a set must have if the number of proper subsets is 1/2 of the total number of subsets.

For example: A = { 4 }

Proper subset : { } (1)

All subsets: { }, { 4 } (2)

1 = 1/2 * 2

Answer: 1 element.