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Need Solution for R.D.  Sharma Maths Class 12 Chapter 30 Probability  Exercise Multiple Choice Questions  Question 34 Maths Textbook Solution.

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Answer:(d)

Hint: You must know the rules of finding probability.

Given: P(A)=\frac{3}{8}, P(B)=\frac{5}{8}, P(A \cup B)=\frac{3}{4}

Solution:

\begin{aligned} &P(A \cup B)=\frac{3}{4} \\ &P(A)+P(B)-P(A \cap B)=\frac{3}{4} \\ &P(A \cap B)=\frac{5}{8}+\frac{3}{8}-\frac{3}{4} \\ &=\frac{5+3-6}{8}=\frac{2}{8} \\ &=\frac{1}{4} \end{aligned}

Also,

\begin{aligned} &P(\bar{A} \cap B)=P(B)-P(A \cap B) \\ &=\frac{5}{8}-\frac{1}{4} \\ &=\frac{5-2}{8}=\frac{3}{8} \end{aligned}

Now,

\begin{aligned} &P\left(\frac{\bar{A}}{B}\right) \times P\left(\frac{A}{B}\right)=\frac{P(A \cap B)}{P(B)} \times \frac{P(\bar{A} \cap B)}{P(B)} \\\\ &=\frac{\left(\frac{1}{4}\right)}{\left(\frac{5}{8}\right)} \times \frac{\left(\frac{3}{8}\right)}{\left(\frac{5}{8}\right)}=\frac{8}{4 \times 5} \times \frac{3 \times 8}{5 \times 8} \\\\ &=\frac{6}{25} \end{aligned}

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