Thursday, September 25, 2014

Three Skullcaps

After being captured by the tribe of the forest, the three explorers were taken to the tribe's chief, who declared that the tribe needed a successor of great wisdom. He showed the captives five skullcaps, three of which were red and the remaining two were green. He commanded the three to line up with their faces toward the wall. On each he placed a red skullcap.

"Now", the chief said, "turn around and look at each other. Whoever can tell me, with a logical explanation, the colour of the skullcap you are wearing will be granted freedom."

The three turned around, looked at each other, and after a long pause one of them said, "I don't know." Two natives impaled him on their spears.

After another pause, the second prisoner stuttered, "I don't know." The two natives threw him into a fire pit.

Immediately, the third man turned a cartwheel, announced, "My skullcap is red," and proceeded to explain.

Amidst the applause of the gathered tribesmen, the chief awarded the explorer vice-chiefdom of the tribe for his wisdom

How did the explorer know that his skullcap was red?

Three Skullcaps Puzzle Solution

At first, any explorer could have guessed the colour of his own skullcap only if the other two wore green skullcaps. Unfortunately, the first explorer admits to not being able to work it out, and is killed.

Then, with two people left it is possible for either explorer to know if he wears a red skullcap only if the other wears green. In that case, he could reason, "The other person wears green, so if I also have a green skullcap, then the first man would have deduced that he was wearing a red skullcap, since there are only two green caps. Therefore my skullcap is, without doubt, red." Of course, this is not the case. Stupidly, the second explorer admits he does not know and is killed as punishment.

After seeing that the other two could not deduce their colours, and believing in their deductive capabilities, the third prisoner was then sure he was wearing a red skullcap.