Q. If $P(A) = P(B) = x\ and\ P(A \cap B) = P\left( A^{'} \cap B^{'} \right) = \frac{1}{3}$, then $x$ is equal to

A) $\frac{1}{2}$
B) $\frac{1}{3}$
C) $\frac{1}{4}$
D) $\frac{1}{6}$
Explanation

(a)
$P\left( A^{'} \cap B^{'} \right) = 1 - P(A \cup B) = \frac{1}{3}$ [given]
$\Rightarrow \ P(A \cup B) = \frac{2}{3}$
$\therefore\ P(A \cup B) = P(A) + P(B) - P(A \cap B)$
$\Rightarrow \ \frac{2}{3} = x + x - \frac{1}{3}\ \Rightarrow \ x = \frac{1}{2}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

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