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Three urns contain 6 red, 4 black; 4 red, 6 black and 5 red, 5 black marbles respectively. One of the urns is selected at random and a marble is drawn from it. If the marble drawn is red, then the probability that it is drawn from the first urn is

Solution

✅ Correct Option: 4

Bayes' theorem. P(Ui)=13P(U_i) = \frac{1}{3} for i=1,2,3i=1,2,3.

P(R∣U1)=610P(R|U_1)=\frac{6}{10}, P(R∣U2)=410P(R|U_2)=\frac{4}{10}, P(R∣U3)=510P(R|U_3)=\frac{5}{10}.

P(U1∣R)=(1/3)(6/10)(1/3)(6/10+4/10+5/10)=615=25P(U_1|R) = \frac{(1/3)(6/10)}{(1/3)(6/10+4/10+5/10)} = \frac{6}{15} = \frac{2}{5}.

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