Logic Puzzle Solution
This is the solution to the previous logic puzzle.
If you haven't read it yet and don't want any spoilers, please start from the previous article.
Shortly after I published this article, I received a comment from suwi saying, "I think I might have figured out the answer." It was so fast that I wondered if they had found the solution almost at the same time they finished reading the problem. suwi also shared some hints on how to solve it in the comments, but unfortunately, I couldn't understand them when I read them. ...Because of that, I was actually secretly doubting them, thinking, "Did suwi really solve it? They did write 'might have' after all..." (← That's incredibly rude of me. I'm sorry! The answer I found the next day was exactly as suwi had said in their first comment.)
I thought of the answer the next day while I was wiping things down.
I wonder what you call that phenomenon where thinking goes better when you're doing simple, mindless tasks like weeding or cleaning than when you're doing nothing at all. Does it have a name? Or perhaps, could it be that I actually have ADHD tendencies and find it easier to concentrate when I'm fidgeting with something like a fidget toy...?
Anyway, enough of that digression. Now, let's look at the solution I came up with.
<Solution 1>
Ask, "Which of the other two is the younger one?"
・If the respondent is the eldest sister: Choose the third sister
・If the respondent is the third sister: Choose the eldest sister
・If the respondent is the second sister: Choose the third sister when in a truthful mood, and the eldest sister when in a lying mood
Since the doors of the eldest and third sisters are both exits, you can get out by opening the door chosen by the respondent, no matter who they are. (I don't know where you're being held, though.)
The same result is obtained with the question, "Which one lies often?"
Conversely, if you ask "Which one is older?" or "Which one sometimes tells the truth?", it would be better to open the door that the respondent did not choose.
Ryujiro found a website ( https://sist8.com/3prc ) that contains the correct answer, so I checked it there. There were two solutions.
The first one is the same as my method. The second one is as follows.
<Solution 2>
Point to another person and ask the respondent, "If I were to ask you 'Is this person the second sister?', would you say 'Yes'?"
・Combinations of respondent and person asked (= 'this person') when the answer is 'Yes'
{Eldest + Second, Second + Eldest, Second + Third, Third + Second}
・Combinations of respondent and person asked when the answer is 'No'
{Eldest + Third, Second + Eldest, Second + Third, Third + Eldest}
Therefore, if the answer is 'Yes', you should choose the door of the other person who is not the one you asked about. If the answer is 'No', you should choose the door of the person you asked about, i.e., 'this person'.
The second solution is confusing because the third sister's words are like a double negative. I wonder what kind of brain someone has to come up with a solution like this.
Now, in the comments section of the previous article, suwi, Pochipico, Takii, Riako, Ryujiro, Nassan, and Shimamura helped me think about it and gave me hints. Thank you. It felt like we were working on it together, and it was a lot of fun.
If you have any other methods, please let me know in the comments. Feedback is also very welcome.
いいなと思ったら応援しよう！
ありがたくいただきます。