Question

$A=\{1,2,\{3,4\left\}\right\}$ number of proper subsets of $A$ is

• A. $16$
• B. $15$
• C. $3$
• D. $6$

Answer 1

The correct option is D $6$

$A=\{1,2,\{3,4\left\}\right\}$

Number of elements in $A,n=3$.

Total number of subsets of $A=2^n=2^3=8$.

Except for set $A$ and null set, all other sets are proper sets.

Hence number of proper subsets $=8-2=6.$