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Need Solution for R.D.Sharma Maths Class 12 Chapter 30 Probability  Exercise 30.5 Question 28 Maths Textbook Solution.

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Answer:Proved

Hint: You must know the rules of finding probability functions.

Given: A and B take turns in throwing two dice,

The first throw 10 being awarded the prize.

Solution: There are only three possible cases, where the sum of number obtained after throwing

2 dice is 10, i.e.[(4,6) , (5,5) , (6,4)]

P( sum \: of \: number\: is 10)=\frac{3}{36}=\frac{1}{12}

P( sum \: of \: number \: is \: not\: 10)=1-\frac{1}{12}=\frac{11}{12}

P(\mathrm{~A} \: winning )=P(10 \: in \: first \: throw)+P(10 \: in\: third \: throw )+\ldots

\begin{aligned} &=\frac{1}{12}+\left(\frac{11}{12} \times \frac{11}{12} \times \frac{1}{12}\right)+\ldots \ldots \\ &=\frac{1}{12}\left[1+\left(\frac{11}{12}\right)^{2}+\left(\frac{11}{12}\right)^{4}+\ldots\right] \\ &=\frac{1}{12}\left[\frac{1}{1-\frac{121}{144}}\right] \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \quad\left[1+a+a^{2}+a^{3}+\ldots=\frac{1}{1-a}\right] \\ \end{aligned}

\begin{aligned} &=\frac{1}{12} \times \frac{144}{23} \\\\ &=\frac{12}{23} \end{aligned}

P(\mathrm{~B} \text { winning })=1-P(\mathrm{~A} \text { winning })=\frac{11}{23}

Now,

\frac{P(\mathrm{~A} \text { winning })}{P(\mathrm{~B} \text { winning })}=\frac{\frac{12}{23}}{\frac{11}{23}}=\frac{12}{11}

Posted by

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