Q. If $A\ and\ B$ are two events such that $P(A \cup B) = \frac{5}{6}$, $P(A \cap B) = \frac{1}{3}and\ P\left( \overline{B} \right) = \frac{1}{3}$,then the value of $P(A)$is

A) $\frac{1}{3}$
B) $\frac{1}{4}$
C) $\frac{1}{2}$
D) $\frac{2}{3}$
Explanation

(c)
Given, $P\left( \overline{B} \right) = \frac{1}{3} \Rightarrow P(B) = \frac{2}{3}$,
$P(A \cup B) = \frac{5}{6},P(A \cap B) = \frac{1}{3}$
Now, $P(A \cup B) = P(A) + P(B) - P(A \cap B)$
$\Rightarrow \frac{5}{6} = P(A) + \frac{2}{3} - \frac{1}{3}$
$\Rightarrow P(A) = \frac{5}{6} - \frac{2}{3} + \frac{1}{3} = \frac{1}{2}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.