There are 5 bags three of which each contains 5 white and 2 black balls, and remaining 2 bags each contains 1 white and 4 black ball; a black ball has been drawn, find the chance that it came from second group.
Choose the correct choice from the following answers:
A) 2/7
B) 6/35
C) 8/25
D) 28/43
E) 3/5
Please go through my solution and suggest any mistake.   Chances of selecting a black ball from group 1: 2/7----------------------Chances of selecting a black ball from group 2: 4/5   Thus combined probability of section of black ball from group 1:   3/5 x 2/7 = 6/35   Thus combined probability of section of black ball from group 2:   2/5 x 4/5 = 8/25   Out of these chances, chance of occurrence of first case : (8/25) / (6/35 + 8/25) = 28/43   28/43
<result>D</result>
There are 5 bags three of which each contains 5 white and 2 black balls, and remaining 2 bags each contains 1 white and 4 black ball; a black ball has been drawn, find the chance that it came from second group.