Test your Critical Thinking and see if you can figure it out.
The first box has two white marbles. The second box has two black marbles. The third box has a white and a black marble.
Boxes are labeled but all labels are wrong!
You are allowed to open one box, pick one marble at random, see its color and put it back into the box, without seeing the color of the other marble.
How many such operations are necessary to correctly label the boxes?