Question

If $A=\{1,2,\{3,4\left\}\right\}$, then the number of non-empty proper subsets of $A$ is

• A. $16$
• B. $15$
• C. $3$
• D. $6$

Answer 1

The correct option is D $6$

Set A has $3$ elements as $3,4$ are combined together as one element.
Number of non empty proper subsets of a set with $n$ elements is $=2^n-2$
So, Number of non empty proper subsets of a set with $3$ elements is $=2^3-2=8-2=6$