Question

Let $A$ and $B$ be two events such that $P(A)=0.3$ and $P(A\cup B)=0.8$. If $A$ and $B$ are independent events. Then, $P(B)$ is equal to

• A. 5/7
• B. 2/3
• C. 1
• D. None of these

Answer 1

Answer: (A)

Let $P(B)=b$, then we have
$P(A\cup B)=P(A)+P(B)-P(A)\cdot P(B)$
(Since $A$ and $B$ are independent events.)
$\therefore 0.8=0.3+b-0.3\times b$
$\Rightarrow b=5/7$