Is this a trick question? Balls into urns probability There are two urns. Urn 1 contains 3 white and 2 red ball, urn 2 one white and two
red. First, a ball from urn 1 is randomly chosen and placed into urn 2. Finally, a ball from
urn 2 is picked. This ball be red: What is the probability that the ball transferred from
urn 1 to urn 2 was white?
My answer is 3/5 - 3W over 5 balls in urn 1 as the second event does not tell me anything to influence which ball was transferred since urn 2 already has a red ball anyways. Hope to know if my reasoning is valid!


A Pretty Straightforward question. Please go through the diagram. Another way to think is if 1W transferred to U2= (1W + 2R) makes U2 = (2R + 2W). Now, # White Balls = # Red Balls . Then P(W)= P(R) = 1/2 for Urn2.
