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It is given that the events $A$ and $B$ are such that $P(A)=\frac{1}{4}, P\left(\frac{A}{B}\right)=\frac{1}{2}$ and $P\left(\frac{B}{A}\right)=\frac{2}{3}$. Then $P(B)$ is
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The correct answer is:
$\frac{1}{3}$
$\frac{1}{3}$
$$
\begin{aligned}
& \frac{P(A \cap B)}{P(B)}=\frac{1}{2}, \frac{P(A \cap B)}{P(A)}=\frac{2}{3} \\
& \text { Hence } \frac{P(A)}{P(B)}=\frac{3}{4} . \quad(\text { But } P(A)=1 / 4) \\
& \Rightarrow P(B)=\frac{1}{3} .
\end{aligned}
$$
\begin{aligned}
& \frac{P(A \cap B)}{P(B)}=\frac{1}{2}, \frac{P(A \cap B)}{P(A)}=\frac{2}{3} \\
& \text { Hence } \frac{P(A)}{P(B)}=\frac{3}{4} . \quad(\text { But } P(A)=1 / 4) \\
& \Rightarrow P(B)=\frac{1}{3} .
\end{aligned}
$$
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