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Provide solution for RD Sharma Maths Class 12 Chapter 30 Probability Exercise 30.3 question 27.

Answers (1)

Answer: \frac{1}{2},\frac{1}{3}

Hint:    P(A \mid B)=\frac{P(A \cap B)}{p(B)}

Given,  A=Both the children are girls

            B=The youngest child is a girl   
            C=At least one child is a girl

Solution:

\begin{aligned} &S=\left\{B_{1} B_{2}, B_{1} G_{2}, G_{1} B_{2}, G_{1} G_{2}\right\} \\ &A=\left\{G_{1} G_{2}, G_{2} G_{1}\right\} \\ &B=\left\{B_{1} G_{2}, G_{1} G_{2}\right\} \\ &C=\left\{B_{1} G_{2}, G_{1} B_{2}, G_{1} G_{2}\right\} \\ &A \cap B=\left\{G_{1} G_{2}\right\} \\ &A \cap C=\left\{G_{1} G_{2}\right\} \\ &P(A)=2 \\ &P(B)=2 \end{aligned}

  1. Required probability P(A \mid B)=\frac{P(A \cap B)}{p(B)}=\frac{1}{2}
  2. Required probability  P(A \mid C)=\frac{P(A \cap C)}{p(C)}=\frac{1}{3}

 

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