Question

If $A$ and $B$ are two disjoint sets $n\left(A\right)=15$ and $n\left(B\right)=10$ find $n\left(A\cup B\right)$ and $n\left(A\cap B\right)$.

Answer 1

Given that, $A$ and $B$ are two disjoint sets

$n\left(A\right)=15$ and $n\left(B\right)=10$

Then,

$n(A\bigcap B)=0$ because$A$ and $B$ both are disjoint

$n(A\bigcup B)=n\left(A\right)+n\left(B\right)-n(A\bigcap B)$

$n(A\bigcup B)=15+10-0$

$n(A\bigcup B)=25$

Hence, this is the answer.