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Three critics review a book. Odds in favour of the book are 5:2, 4:3and 3:4 respectively for three critics. Find the probability that eh majorityare in favour of the book. |
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Answer» Let A, B, C denote the evets that the book be favoured by the first, second and third critic respectively. Then, `P(A)=5/7, P(B)=4/7, P(C)=3/7`, `P(bar(A))=(1-5/7)=2/7, P(bar(B))=(1-4/7)=3/7` and `P(bar(C))=(1-3/7)=4/7`. Required probability = P(2 criticec favour the book or 3 critics favour the book) = P (2 critics favour the book) + P (3 critics favours the book) = P[{A and B and not C} or {A and C and not B} or {B and C and not A}]+P (A and B and O) `=P(A nn B nn bar(C))+P(A nn bar(B) nn C)+P(bar(A) nn B nn C)+P(A nn B nn C)` `={P(A)xxP(B)xxP(bar(C))}+{P(A)xxP(bar(B))xxP(C)}+{P(bar(A))xxP(B)xxP(C)}+{P(A)xxP(B)xxP(C)}` `=(5/7xx4/7xx4/7)+(5/7xx3/7xx3/7)+(2/7xx4/7xx3/7)+(5/7xx4/7xx3/7)` `=(80/343+45/343+24/343+60/343)=209/343`. Hence, the required probability is `209/343`. |
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