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Logic and Stamps (Posted on 2004-07-31) Difficulty: 4 of 5
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?

See The Solution Submitted by Brian Smith    
Rating: 2.5000 (8 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
logically | Comment 11 of 18 |
there can be only one answer; 'A'" and 'C' have the same colours, i.e., 'A": red/red, 'B': red/red or 'A": green/green, 'B': green/green.  This leaves 'B' with the other colour and the same colour in the moderator's pocket.
  Posted by Robert Botwood on 2004-08-10 22:56:44
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