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There are 25 girls and 15 boys in class XI and 30 boys and 20 girls in class XII. If a student chosen from a class, selected at random, happens to be a boy, find the probability that he has been chosen from class XII. |
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Answer» <P> Solution :LET `E_1`= The student is choosen from class XI.`E_2` The student is choosen from class XII. A= The student is a boy.`P(E_1)=P(E_2)=1/2` `P(A//E_1)=15/40=3/8` P(A//E_2)=30/50=6/10` We WENT to find `P(E_2//A)`. By Baye.s theoren `P(E_2|A)=(P(E_2)P(A//E_2))/(P(E_1)P(A//E_1)+P(E_2)P(A//E_2))` `=(1/2cdot 6/10)/(1/2cdot3/8+1/2cdot6/10)=(6/10)/((15+24)/40)=24/39=8/13` |
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