Sunday, 27 January 2008

Brain teaser 5

Imagine that you have 3 boxes, one containing 2 black marbles, one containing 2 white marbles, and the third, 1 black marble and 1 white marble. The boxes were labeled for their contents - BB, WW and BW - but someone has switched the labels so that every box is now incorrectly labeled. You are allowed to take one marble at a time out of any box, without looking inside, and by this process of sampling you are to determine the contents of all three boxes. What is the smallest number of drawings needed to do this?

1 comment:

Gary said...

3 if you are lucky.
pick from box 1 - Black
pick from box 2 - Black
pick from box 2 again - Black

therefore box1 is BW, box2 is BB, box3 is WW