Question

If $U=\{1,2,3,4,5\}$ and $A=\{2,5\}$, then $A^{\prime }=$

• A. $\{2,5\}$
• B. $\{1,3,4\}$
• C. $\varphi$
• D. $\{1,2,3,4,5\}$

Answer 1

The correct option is B $\{1,3,4\}$

The complement of a set $A$ is the set of all elements in the universal set $U$ which are not in $A$.
Thus, if $U=\{1,2,3,4,5\}$ and $A=\{2,5\}$, then the elements 1, 3 and 4 are the only elements of $U$ which are not in $A$.
$⟹A^{\prime }=\{1,3,4\}$