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 white ball has been drawn, find the chance that it came from first group.
Choose one:	A) 2/7	B) 6/35	C) 8/25	D) 75/89	E) 3/175
Please go through my solution and suggest any mistake.   Chances of selecting a white ball from group 1: 5/7----------------------Chances of selecting a white ball from group 2: 1/5   Thus combined probability of section of white ball from group 1:   3/5 x 5/7 = 3/7   Thus combined probability of section of white ball from group 2:   2/5 x 1/5 = 2/25   Out of these chances, chance of occurrence of first case : (3/7) / (3/7 + 2/25) = 75/89   75/89
<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 white ball has been drawn, find the chance that it came from first group.