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Need Solution for R.D.Sharma Maths Class 12 Chapter 30 Probability  Exercise 30.4 Question 24 Maths Textbook Solution.

Answers (1)

Answer: No pair is independent

Hint: Probability=\frac{No\: of\: outcomes}{Total\: outcomes}

Given: Two dice are thrown together and the total score is noted. The event E,F and G are “a  total 4”, “a total of 9 or more” and “ a total divisible by 5”

Solution:

S=\left\{\begin{array}{l} (1,1),(1,2),(1,3),(1,4),(1,5),(1,6), \\ (2,1),(2,2),(2,3),(2,4),(2,5),(2,6), \\ (3,1),(3,2),(3,3),(3,4),(3,5),(3,6), \\ (4,1),(4,2),(4,3),(4,4),(4,5),(4,6) \\ (5,1),(5,2),(5,3),(5,4),(5,5),(5,6), \\ (6,1),(6,2),(6,3),(6,4),(6,5),(6,6) \end{array}\right\}

\begin{aligned} &n(S)=36 \\ &E=a \text { total of } 4 \\ &\quad=\{(1,3),(2,2),(3,1)\} \\ &\text { ie, } n(E)=3 \end{aligned}

F=a\: total\: of\: 9\: or\: more

       =\left\{\begin{array}{l} (3,6),(4,5),(4,6),(5,4),(5,5) \\ (5,6),(6,3),(6,4),(6,5),(6,6) \end{array}\right\}

i.e,n(f)=10

G=a\: total\: divisible\: by\: 5

      =\left\{\begin{array}{l} (1,4),(2,3),(3,2),(4,1), \\ (4,6),(5,5),(6,4) \end{array}\right\}

i.e,n(G)=7

Now,

          \begin{aligned} &P(E)=\frac{3}{36}=\frac{1}{12} \\ &P(F)=\frac{10}{36}=\frac{5}{18} \\ &P(G)=\frac{7}{36} \end{aligned}

Also,

          \begin{aligned} &E \cap F=\varnothing, E \cap G=\varnothing \\ &F \cap G=\{(4,6),(5,5),(6,4)\} \\ &\text { ie, } n(F \cap G)=3 \\ \end{aligned}

\begin{aligned} &P(F) \times P(G)=\frac{5}{18} \times \frac{7}{36} \\ \end{aligned}

                                \begin{aligned} &=\frac{35}{648} \\ &\neq \frac{3}{36} \end{aligned}

i.e,P(F)\times P\left ( G \right )\neq P\left ( F\cap G \right )

So, no pair is independent.

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infoexpert21

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