- You have three boxes, one containing 2 white marbles, one containing 2 black marbles, and a third containing one balck marble and one white marble. The boxes were labeled as WW, BB, and BW respectively according to their contents. For some reason, the labels were switched and every box is now wrongly labeled. Can you determine the contents of all the boxes from the color of one marble that you draw from a particular box without looking inside?
Answer
If you draw from the box labeled BW a black marble then since it is wrongly labeled, it must have 2 black marbles. The box labeled WW contains a white marble and a black marble and the box labeled BB contains 2 white marbles.
If the marble drawn from BW labeled box is white then this box has to contain 2 white marbles. The box labeled WW contains 2 black marbles and the BB labeled box contains one black marble and one white marble.