A Fork in the Road

Dec 13, 2014

RAY: It was a dark and stormy night. You're on Isla Nubar off Costa Rica. You're in your Nissan Pathfinder and you're being pursued by Tyrannosaurus Rex.

Your only hope is to get off the island. Otherwise, you're going to be passing through the digestive system of said Rex. You have to make it to the dock because that's where your little boat is. If you don't make it to the dock --

TOM: You're done for!

RAY: The pterodactyls are circling overhead. You're driving along, and you come to a fork in the road. One road takes you to certain death because you don't know where that goes. The other one takes you to the dock where your little boat awaits.

Sitting at the fork are two guys. Now, on this island there are either liars or truth tellers. You know one road leads to death; the other to the dock. You can ask one question of either one of the two guys. One of these guys is a liar and one of them is a truth teller.

You have no way of identifying them. Is there one question you can ask of either of these guys that will unquestionably get you on the right road to the dock?


RAY: Here's the question I would ask. I would look at one of the guys and say, "If I were to ask the other guy which road takes me to the dock, what would he say?"

If you ask the truth teller, it's pretty simple, right? The truth teller will say the liar is going to tell you to take this road, which is -- which is obviously the wrong road because that guy's what?

TOM: He's a liar.

RAY: Right. Now you ask the liar the same question, and he has to point to the same road—because otherwise he'd be telling the truth. Do we have a winner?

TOM: We do! Congratulations to our winner, Elizabeth Caprini from Naples, New York.

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