MathDB
2000 Guts #43: Picking marbles from a box

Source:

October 25, 2014
probability

Problem Statement

Box A contains 33 black and 44 blue marbles. Box B has 77 black and 11 blue, whereas Box C has 22 black, 33 blue and 11 green marble. I close my eyes and pick two marbles from 22 different boxes. If it turns out that I get 11 black and 11 blue marble, what is the probability that the black marble is from box A and the blue one is from C?