Three philosophers take an afternoon nap out in the countryside. A fool happens by and for amusement draws an X on all of the philosophers foreheads. When the philosophers wake up, they all start laughing at each other for having marks on their heads. It doesn't take long for one of the men to stop laughing. How did the man deduce that he also had a mark on his head?
Hint: A philosopher wouldn't laugh if he knew he had a mark. The philosophers are laughing because each thinks the other two must be laughing at each other.
Answer: Call the men A, B and C. A assumes he has no mark and B and C are laughing at each other. If that were the case then B and C would realize very quickly that they are laughing at each other's mark and they'd stop laughing. Since B and C are still laughing, A can surmise that he must have a mark.
No comments:
Post a Comment