Q.

Bag B1 contains 6 white and 4 blue balls, Bag B2 contains 4 white and 6 blue balls, and Bag B3 contains 5 white and 5 blue balls. One of the bags is selected at random and a ball is drawn from it. If the ball is white, then the probability, that the ball is drawn from bag B2, is :          [2025]

1 25  
2 415  
3 23  
4 13  

Ans.

(2)

Consider the events, E1: Bag B1 is selected, E2: Bag B2 is selected, E3: Bag B3 is selected

A : Ball drawn is white. Then P(E1)=P(E2)=P(E3)=13

P(A/E1)=610,P(A/E2)=410,P(A/E3)=510

Required probability

P(E2A)=P(E2)P(AE2)P(E1)P(AE1)+P(E2)P(AE2)+P(E3)P(AE3)

                     =13×410(13)(610)+(13)(410)+(13)(510)=430630+430+530=415