Symbiosis National Aptitude Test SNAP 2014 Paper

A and B are mutually exclusive and exhaustive events with
P(A ∩ B) = 0, P(A ∩ B) = 1
we know that
P(A ∩ B) = P(A) + P(B) – P(A ∩ B)
Þ 1 = P(A) + 3P(A)
⇒ P (A) = $\frac{1}{4}$
∴ P (B) = $\frac{3}{4}$
Hence, $\mathit{P}\left(\stackrel{-}{\mathit{B}}\right)$ =1 - P(B) = $1-\frac{3}{4}$ = $\frac{1}{4}$