2000 Guts #43: Picking marbles from a box
Source:
October 25, 2014
probability
Problem Statement
Box A contains black and blue marbles. Box B has black and blue, whereas Box C has black, blue and green marble. I close my eyes and pick two marbles from different boxes. If it turns out that I get black and blue marble, what is the probability that the black marble is from box A and the blue one is from C?