The door riddle
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duckking2001 — 10 years ago(November 16, 2015 04:08 AM)
Based on the scenario in the film it's impossible for her to find the right answer.
One head on the bottom tells her that one door leads to the castle and one door leads to certain doom. The other head on the bottom tells her that they don't know which one is which, to ask the top heads.
She doesn't know if either of them is lying, so she doesn't even know if either door leads to the castle. She can only ask the top heads about where one door leads, so she can't verify this scenario to be true until after she makes her choice. In the event that she can ask multiple questions, she still won't be able to confirm this. I'll get to that later.
If both doors led to doom, the liar would still tell her one of them led to the castle, so she would get the lie either way from her question and she wouldn't know until it was too late.
Next, one of the top heads tells her that she can only ask one question. The other top head tells her one always tells the truth and one always lies.
If head two is telling the truth, then head one is the liar and she can ask more than one question. In that case she can confirm that by asking another question, but that will only prove the first head is a liar, and not whether the second head is true.
Head two could be lying about one of them telling the truth and they both could be liars. Again there is no way to prove that, other than to make the choice and see which one it was afterwards.
*Here's a ***in' spoiler: Everybody dies. -
anonymous1235 — 10 years ago(January 18, 2016 11:19 AM)
What do you mean exactly? Do you mean the premise of the riddle can't be taken at face value (especially since the guards explained the rules to begin with)? Or that the riddle is inherently unsolvable on the face of it? Because this is a famous riddle and Sarah's logic was sound.
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anonymous1235 — 10 years ago(January 21, 2016 01:50 PM)
You still can't know who is lying no matter what you ask.
This is technically true. But, keep in mind, your goal is to find out which
door
is which, not which
guard
is which. Think about what answer Sarah would get from each guard with the question she asks. She's either asking a truthful person about what a liar would say or asking a liar about what a truthful person would say. The answer's going to be a lie either way. -
tnsprin-2 — 9 years ago(May 02, 2016 09:47 AM)
Although correctly explained in this thread, it is INCORRECTLY described at the moment in the FAQ section. No mention of asking the one guard what the other would say. FAQ is currently locked so can't suggest a correction there.
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iminheatlikeacat — 9 years ago(July 28, 2016 12:11 PM)
No you're not! Break it down easier:
Jareth is standing in front of a door that leads to freedom. Jareth always lies.
Sarah is standing in front of a door that leads to certain death. Sarah always tells the truth.
You walk up to them and need to get to freedom. You and they both know that one of them will always tell the truth and one of them will always lie.
If you ask the question "Which door leads to freedom?" Jareth will lie (because he always lies) and point to the door behind Sarah (which leads to certain death). Sarah will tell the truth (because she always tells the truth) and point to the door behind Jareth (which leads to freedom.) So you get both pointing at each others door and it doesn't get you any closer to freedom.
If you ask the question "Which door would the other one tell me leads to freedom?" Sarah will tell the truth and knowing Jareth always lies, would point to the door behind Sarah which leads to certain death. Jareth will lie and knowing Sarah always tells the truth would also point to the door behind Sarah because Sarah would not tell you that the door behind her leads to freedom when it leads to certain death.
Therefore, both of them are now pointing at the door behind Sarah so you know the safe option is the door behind Jareth. Hope that makes sense!?