1. Balls

Suppose there are two bags, bag A and bag B, each containing three balls. Bag A contains three red balls and Bag B contains two red balls and one green ball. One of the bags is selected at random and two balls are taken out. Both are red. The colour of the two balls gives us information about which bag has been chosen.
Calculate the probability that two red balls were drawn:
(a) given that Bag A was chosen, P(RR|A); and
(b) given that Bag B was chosen, P(RR|B)

Could someone explain how to solve this problem?

2. Originally Posted by Bulbagarden
Suppose there are two bags, bag A and bag B, each containing three balls. Bag A contains three red balls and Bag B contains two red balls and one green ball. One of the bags is selected at random and two balls are taken out. Both are red. The colour of the two balls gives us information about which bag has been chosen.
Calculate the probability that two red balls were drawn:
(a) given that Bag A was chosen, P(RR|A); and
(b) given that Bag B was chosen, P(RR|B)

Could someone explain how to solve this problem?
Try drawing a tree diagram for each case.