You are traveling alone in the woods, and are lost. On the verge on dehydration, you come across 2 doors. Standing in the way of the 2 doors are 3 trolls. There is a sign hanging above them:
“Behind one of these doors, is death. Behind the other, is freedom. You MUST choose a door. Guarding the doors are 3 trolls. One troll will always lie. Another will always tell the truth. The remaining troll alternates between telling the truth and lying (If the last question he got asked resulted in him lying, then the next question will result in him telling the truth). You may ask 1 question. You can ask it one troll, 2 trolls or all 3 trolls. Then, you may choose your door. Think carefully.”
What question can you ask and to how many trolls do you ask it to, that will result in your freedom?
Or is it impossible to extract the information you need with this scenario?
Suppose the freedom door is door A, the death door is door B, just to make it easier to describe.
One solutgion: Ask all three trolls: “If I had asked you an hour ago which door leads to freedom, what would you have said?”
The truth-telling troll will think: I would have said Door A, and I tell the truth, so now I say Door A.
The liar-troll will think: I would have lied (said Door B), but now I also lie, so I say Door A.
The alternator troll may say either A or B.
So, you poll the three: the results will be either AAB or AAA; there will be at least two (and possibly all three) saying the same door, and that’s the correct one.
There are about ten zillion variations on this old chestnut.
There’s another version of this riddle with only two trolls (no alternating guy.) Where you can only ask one guy one question. The two solutions I know of for that are:
If I were to ask the other guy which door to take, what would he tell me? (Then go in the opposite door.)
or
If I were to ask you which door to take, what would you tell me? (And go where they say.)
lunapark, you ask all three trolls. The truth telling troll says Door A (correct), the lying troll says Door B (not correct) and the third troll could say either A or B, depending on his whim at the time… So? How does this tell you which door to use.
Manta, how about you confine this to one topic rather than branching out?