Question

The number of non-empty proper subsets of a set A is 0 then n(A)=______

Answer 1

Number of non - empty proper subsets of a set with $n$ elements is $=2^n-2$
Given, for a set A
$2^n-2=0$
$=>2^n=2$
$=>n=1$
So, $n\left(A\right)=1$