A bag A contains 1 white and 6 red balls. Another bag contains 4 white and 3 red balls. One of the bags is selected at random, and a ball is drawn from it, which is found to be white. Find the probability that the ball is drawn is from bag A.
Let R : Red ball
W : White ball
A : Bag A
B : Bag B
Assuming, selecting bags is of equal probability i.e. 
We want to find P(A|W), i.e. the selected white ball is from bag A
Conclusion: Therefore, the probability of selected white ball is from
bag A is 
1