Let $X$ and $Y$ be two events such that $P(X \cup Y) = P(X) \cap P(Y)$. Statement 1: $P\left(X \cap…
Let $X$ and $Y$ be two events such that $P(X \cup Y) = P(X) \cap P(Y)$.
Statement 1: $P\left(X \cap Y^{\prime}\right) = P\left(X^{\prime} \cap Y\right)$.
Statement 2: $P(X) P(Y) = 2 P(X \cap Y)$.
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Statement 1 is false, Statement 2 is true.
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Statement 1 is true, Statement 2 is true, Statement 2 is not a correct explanation of Statement 1.
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Statement 1 is true, Statement 2 is false.
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Statement 1 is true, Statement 2 is true; Statement 2 is a correct explanation of Statement 1.
Solution
Let $X$ and $Y$ be two events such that
$
P(X \cup Y)=P(X \cap Y)
$
We know
$
$\begin{aligned}
& P(X \cup Y)=P(X)+P(Y)-P(X \cap Y) \\
& P(X \cap Y)=P(X)+P(Y)-P(X \cap Y) \\
& \text{(from }(1) \\
& \Rightarrow P(X)+P(Y)=2 P(X \cap Y)
\end{aligned}$
$
Hence, Statement $-2$ is true.
Now, $P\left(X \cap Y^{\prime}\right)=P(X)-P(X \cap Y)$
and $P\left(X^{\prime} \cap Y\right)=P(Y)-P(X \cap Y)$
This implies statement $-1$ is also true
Asked in: JEE Main 2012 (07 May Online)
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