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 , i.e. the selected white ball is from bag :
= Probability of A depending on W.
= Probability of A
= Probability of B
= Probability of B depending on W.
Therefore, the probability of selected white ball is from
bag is