Question

The number of proper subsets of the set $\{1,2,3\}$ is ___.

• A. 8
• B. 7
• C. 6
• D. 5

Answer 1

The correct option is B

7

A set of $n$ elements has $2^n$ subsets.
Every set is a subset of itself.
Thus, the number of proper subsets of a set is $2^n-1$ subsets.
The set $\{1,2,3\}$ has 3 elements and hence, $2^3-1=7$ proper subsets.