Question

Bag I contains 3 black and 4 white balls and bag II contains 4 black and 3 white balls. Now an unbiased die throws, if number 1 or 3 shows on die then a ball is drawn from bag I otherwise from bag II. Find the probability that the ball so drawn is black.

Answer 1

Number of total balls in I bag 3 + 4 = 7, where 3 are black and 4 are white. 

Number of balls in II bag = 4 + 3 = 7, 

where 4 are black and 3 are white. 

Total number of result on throwing a die 

S = {1,2, 3,4, 5, 6} 

Let E₁ be the event to get 1 and 3