Archive for October 2005

Free the Kodo

Six people are trying to rescue a Kodo being held hostage by a psychotic goblin. They meet with the goblin and are made to sit on the outside of a circle facing in towards each other. Every one of them has a green or red disk stuck to their backs. There are three red and three green disks. Each person has the ability to know the colour of the disk on the person on his left and the colour of the 2 people to his right. You also know that the person on your left is cheating and knows the colour of one person on his left and the colour of three people to his right and that only those sitting next to this cheater know he is cheating (that is, you and one other person). You see green to your left, green on your right and red second on your right.

If someone correctly guesses the colour of the disk on their back, the Kodo will be freed. However, if you guess wrong, a Dire Devilsaur will be set loose instead. Thirty-two dire minutes pass, and everyone is still silent. Then you open your mouth and say your colour and the Kodo is freed. What colour was your disk?

You are to assume that everyone wants to free the Kodo (which is cute, among other things) and that no one wants to release the Dire Devilsaur (who will most likely eat everyone except his goblin master, after finishing off the Kodo). You’re all on the same team – that is, no one will deliberately jeopardize the safety of the group or the Kodo. You all want to go home, with the Kodo, so as soon as someone knows the answer with 100% certainty, they will say it. Additionally, no communication of any form is allowed between the people (or the Kodo, or the Devilsaur), other than the knowledge of disk colours. The only thing you’re allowed to communicate is your guess, and it may only be directed at the goblin.

I think I’ve covered everything this time. Jon, feel free to try and find an exploitable loophole. Solution Monday afternoon.