Question

A and B are two candidates seeking admission to IIT. Probability of A getting selected is $0.5$ and that of A and B both being selected is $0.3$. What is the probability of B being selected?

Answer 1

$P(A\cup B)=P\left(A\right)+P\left(B\right)-P(A\cap B)$
$P(A\cup B)=0.5+P\left(B\right)-0.3$
$P(A\cup B)=0.2+P\left(B\right)$
$P(A\cup B)le1$
$0.2+P\left(B\right)\le 1$
$P\left(B\right)\le 0.8$