A moderator takes a set of 8 stamps, 4 red and 4 green, known to three logicians, and affixes two to the forehead of each logician so that each logician can see all the other stamps except those two in the moderator's pocket and the two on his or her own head. He asks them in turn if they know the colors of their own stamps:
1. A: "No"
2. B: "No"
3. C: "No"
4. A: "No"
5. B: "Yes"

What are the colors of B's stamps?

B has two of the same color. there is not enough information to see which color it is.  If A had 2 of the same color, and B had two of the color, and C and both colors, the other two colors could still be in the pocket of the moderator. 

Posted by Pete Za on 2004-08-08 17:37:36