Q.

Bag A contains 3 white, 7 red balls and bag B contains 3 white, 2 red balls. One bag is selected at random and a ball is drawn from it. The probability of drawing the ball from bag A, if the ball drawn is white, is                  [2024]

1 310  
2 14  
3 19  
4 13  

Ans.

(4)

Let E1 be the event that bag A is selected, E2 be the event that bag B is selected and E be the event that white ball is drawn.

  P(E1)=P(E2)=12,  P(EE1)=310,  P(EE2)=35

Required probability,

P(E1E)=P(E1)·P(EE1)P(E1)·P(EE1)+P(E2)·P(EE2)

=12×31012×310+12×35=13