Question

$U$ represents the set of students in class $8$ and $n\left(U\right)=35$. A is the set of students in the class $8$ who have to wear spectacles and $n\left(A\right)=18$.

State the value of $n\left(A^{\prime }\right)$

Answer 1

$U$ represents the set of students in class $8$.

$\Rightarrow$ $n\left(U\right)=35$

$A$ represents set of students in class $8$ who have to wear spectacles.

$\Rightarrow$ $n\left(A\right)=18$

$A^{\prime }$ represent the set of students in class $8$ who don't wear spectacles.

$\Rightarrow$ $n\left(A^{\prime }\right)=n\left(U\right)-n\left(A\right)$

$\Rightarrow$ $n\left(A^{\prime }\right)=35-18$

$\Rightarrow$ $n\left(A^{\prime }\right)=17$