Probability Ques 70
Let $A$ and $B$ be two events such that $P(A)=0.3$ and $P(A \cup B)=0.8$. If $A$ and $B$ are independent events, then $P(B)=\ldots$.
(1990, 2M)
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Answer:
Correct Answer: 70.$(\frac{5}{7})$
Solution:
Formula:
Set theoretical notation of probability and some important results:
- $P(A \cup B)=P(A)+P(B)-P(A) P(B)$, as $A$ and $B$ are independent events.
$\Rightarrow 0.8=(0.3)+P(B)-(0.3) P(B) $
$\Rightarrow 0.5=(0.7) P(B) \Rightarrow P(B)=\frac{5}{7}$
BETA
