Conditional probability · Urn · difficulty 3 of 5
Looking back at the first ball
An urn holds 3 red and 2 blue balls. You draw two balls, one after the other, at random without replacement, and set them aside without looking. A friend looks and tells you only that the second ball drawn is red. What is the probability that the first ball drawn was red?
Answer with a probability. First lock in a gut guess with an 80% range, then solve it properly, then watch a simulation settle on the truth.
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