You are at one end of a hall blindfolded. At the other end are Alex and Bert. You are allowed to ask any yes or no questions you want, but only one of them will respond. They are standing next to each other and their voices are identical, so you have no way of telling which one responded by sound alone.

Using as few questions as possible, find out the type of each Alex and Bert and who answered your last question.

(In reply to number of liars and knights by rerun141)

I'm not exactly sure why you must double the questions half of the time (I probably haven't tried hard enough), but I think that you could fix this problem with another question. Ask this: "What would you say if I asked you whether Alex and Bert are the same type?" Then, depending on the answer, you could ask different questions. I'll assume that you only count the maximum possible questions for all the cases (just like I'll assume there are no knaves). I hope I'm helping somehow, but I'm too tired right now to do the real solving myself.

Posted by Tristan on 2003-12-30 19:42:43