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Provide Solution For  R.D. Sharma Maths Class 12 Chapter 30 Probaility  Exercise Multiple Choice Questions Question 32 Maths Textbook Solution.

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Answer:(c)

Hint: You must know the rules of finding probability.

Given:P(A)=\frac{2}{5}, P(B)=\frac{3}{10}, P(A \cap B)=\frac{1}{5}

Solution:

\begin{aligned} &P(\bar{A})=1-P(A)=1-\frac{2}{5}=\frac{3}{5} \\\\ &P(\bar{B})=1-P(B)=1-\frac{3}{10}=\frac{7}{10} \\\\ &\therefore P(A \cup B)=P(A)+P(B)-P(A \cap B) \\ \end{aligned}

\begin{aligned} &=\frac{2}{5}+\frac{3}{10}-\frac{1}{5} \\\\ &=\frac{4+3-2}{10}=\frac{5}{10} \\\\ &=\frac{1}{2} \end{aligned}

Also,

\begin{aligned} &P\left(\frac{\bar{A}}{\bar{B}}\right) \times P\left(\frac{\bar{B}}{\bar{A}}\right)=\frac{P(\bar{A} \cap \bar{B})}{P(\bar{B})} \times \frac{P(\bar{A} \cap \bar{B})}{P(\bar{A})} \\\\ &=\frac{\left(\frac{1}{2}\right)}{\left(\frac{7}{10}\right)} \times \frac{\left(\frac{1}{2}\right)}{\left(\frac{3}{5}\right)}=\frac{10}{2 \times 7} \times \frac{5}{3 \times 2} \\\\ &=\frac{25}{42} \end{aligned}

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