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Need solution for RD sharma maths class 12 chapter 30 probablity exercise Very short answer question, question 15

Answers (1)

The value of  P(A\cup B)=0.75

Hint:

Using the formula,

P(B | A) = \frac{P(A\cap B)}{P(A)}  first find P(A\cap B)

Then using the relation, P(A \cup B)=P(A)+P(B)- P(A\cap B),

Find the required value

Given:

P(A) = 0.3

P(B) = 0.6

P(B|A) = 0.5

Explanation:

We know ,

\begin{aligned} &P(B \mid A)=P(A \cap B) \\ &P(B / A)=\frac{P(A \cap B)}{P(A)} \\ \end{aligned}

\begin{aligned} &\Rightarrow 0.5=\frac{P(A \cap B)}{0.3} \\ &\Rightarrow P(A \cap B)=0.5 \times 0.3 \\ &\Rightarrow P(A \cap B)=0.15 \end{aligned}

We know ,

\begin{aligned} P(A \cup B) &=P(A)+P(B)-P(A \cap B) \\ &=0.3+0.6-0.15 \\ &=0.75 \end{aligned}

Hence , P(A\cup B)=0.75

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