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Need solution for RD Sharma maths class 12 chapter Probability exercise 30.7 question 19

Answers (1)

Answer:

 \frac{28}{45}

Hint:

 Use Baye’s theorem.

Given:

 In group of 400 people 160 smoke and non-vegetarians, 100 smoke and vegetarians. The probability of getting chest disease 35%, 20%, 10% respectively. A person chosen from group at found suffering. Find probability selected person smoke non vegetarian.

Solution:

Let us denote group of smoker and non-vegetarian as A.

B = smoker and non-vegetarian

C = no smoker and vegetarian

No of people in group A = 160;

P(A)=\frac{160}{400}

No of people in group B = 100;

P(B)=\frac{100}{400}

No of people in group C = 400 - 260 = 140;

\begin{aligned} &P(C)=\frac{140}{400}\\ &P(D_A)=35%\\ &P(D_B)=20%\\ &P(D_C)=10%\\ \end{aligned}

Probability of disease person from group A is

Using Baye’s theorem we get

\begin{aligned} &P(\text { smoker and vegetarian })=\frac{P(A)\times P(D_A)}{P(A)\times P(D_A)+P(B)\times P(D_B)+P(C)\times P(D_C)}\\ &=\frac{\frac{2}{5}\times 35%}{\frac{2}{5}\times 35%+\frac{1}{4}\times 20%+\frac{7}{20}\times 10%}\\ &=\frac{\frac{2}{5}\times 35}{\frac{2}{5}\times 35+\frac{1}{4}\times 20+\frac{7}{20}\times 10}\\ &=\frac{14}{14+5+\frac{7}{2}}\\ &=\frac{14}{\frac{19+7}{2}}\\ &=\frac{28}{38+7}\\ &=\frac{28}{45} \end{aligned}

Posted by

Gurleen Kaur

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