The Logic Puzzle You Can Only Solve with Your Brightest Friend
6
From Nautil.us
You’ve been caught snooping around a spooky graveyard with your best friend. The caretaker, a bored old man fond of riddles (and not so fond of trespassers), imprisons each of you in a different room inside the storage shed, and, taking your phones, says, “Only your mind can set you free.” To you, he gestures toward a barred window. Through it, you can see 12 statues. Out of your friend’s window, which overlooks the opposite side of the graveyard, she can see eight. Neither of you know the other’s count.
The caretaker tells you each, individually, that together you can see either 18 or 20 statues. Unfortunately, there’s no way to tell your friend how many you can spot. The only way for you both to escape is for one of you to give the total number of visible statues. Get it wrong, and neither of you ever leave. The caretaker asks you each one at a time, once a day, and you can choose to answer or to pass. Both of you know that you’re always asked first. If you both pass on a given day, the question—are there 18 or 20?—is posed to each of you again the next day, and the next, and so on, until you get it right or wrong. The caretaker cackles, “If you need me, I’ll be out preparing your graves.”*
How do you escape?
Answer Here: http://nautil.us/blog/-the-logic-puzzle-you-can-only-solve-with-your-brightest-friend
(I couldn’t/wouldn’t take the time to figure it out–but it all made complete sense once I read the answer)
- 9 comments, 18 replies
- Comment
Haven’t read it yet but I’d say you found a new favorite site for yourself!
@lseeber I have!
This puzzle needs a more convincing setup. My brain is busy poking holes in the flimsy premise. Spooky (presumably rundown) graveyard, adjacent rooms in the same (presumably typical and rundown) shed, looking through (presumably standard, albeit barred, glass) windows, apparently no other visitors to the graveyard, etc… No mention of why I’m unable to communicate to my friend nor escape under my own power. Is the place sound proof? Can I not knock on the wall, stomp my feet, or yell out the window? Am I somehow restrained?
It specifically mentions the phones were taken which seems to imply I would still have some range of movement in at least my hands and/or ability to speak to use voice commands. This also implies there is some connectivity in this location for phones to be an issue. My spouse and mother can see my location on Google maps, so I hope he turned the phone off…Even still, they’d see my last location, not to mention authorities can get my last cell tower ping, so…
I guess I’m saying I wouldn’t even entertain the groundskeeper and his silly game because A) he probably can’t be trusted, and B ) there seem to be several options for escape that don’t rely on the word of a sketchy stranger.
This is why I can’t stand horror films. Playing along or doing as the killer says is generally not your best option for survival. “Oh neat, you passed my test. Too bad I’m going to kill you anyway. LOL Sorry!”
Seems better to just say we would each win a million dollars if we followed the rules of not communicating directly with one another, no outside help (no google), and only had 5 total answers/moves to figure it out. Maybe then it would be worth scratching my head over.
Lord, @medz. It’s PRETEND man! You are taking this a little seriously…but to extrapolate your million-dollar prize…what is your life worth?
@medz or you could wait for Scooby and the gang to show up for the big reveal!
/giphy Scooby Doo
@tinamarie1974 Nah, it’s always the groundskeeper, not the caretaker.
@therealjrn my life is worth enough not to trust some creep to keep his word.
@cinoclav groundskeeper v caretaker. Kinda the same thing…
@medz @therealjrn It sounds like an earlier version of this puzzle used an evil king and trees in his courtyard.
In that scenario there would be no cell phones, or the U.S. may not be willing to invade a country just because two people go missing. Your entrapment could be a bit more substantial, too.
I’m doomed. All of my friends are the type who would think: “Well, there’s a 50/50 chance either way.” and guess wrong. Maybe I need smarter friends. Or to avoid spooky graveyards. Or to carry a second concealed phone.
@rockblossom where you gonna conceal that phone?
@tinamarie1974 Flip phones are small, so they can go … many places.
@rockblossom @tinamarie1974 Really, because I can only think of, like, two.
@Limewater @rockblossom i can think of three. Did you count cleavage?
@Limewater Do they include the watch pocket of a pair of jeans and inside the top of a boot? Because that’s where I usually carry mine.
This makes my head hurt. I read the explanation and I don’t get it.
/giphy fucking stupid
@RiotDemon Oh, easy. It means that you and a friend can figure out the logic of the numbers while also believing that the caretaker will actually let you go when you know who he is and where he works.
It makes sense and all but the chances I and a friend would figure that out while held captive are approximately the chances this creep would stay true to his word if we did. Which is what I believe @rockblossom said just above me.
@djslack Well, that. And you are smart enough to figure out the puzzle, but spend days in a TOOL SHED without finding something that could be used to get out.
I must be missing something - you’re told there are either 18 or 20 items and one of two people has to give the correct number to leave, so if you guess 18 today, you just guess 20 the following day, eh? (Assuming you don’t just kick out some boards and clamber out - it’s just a shed, for god’s sake.) Shouldn’t it be that BOTH of you have to get the correct answer? Though again, you’d have to be pretty unlucky to be in for more than two days.
@aetris
anyone gets it wrong, you never leave
The cat is either dead or alive
and it only lives if you guess right
So what it should say is that if either of you guess right you can leave, unless either of you guess wrong, in which case you can’t leave.
It’s an inverted version of the prisoner’s dilemma, but it needs to be phrased a little better. As it stands my guess is the caretaker’s name is either Doug or Dinsdale Piranha.
Another logic puzzle:
The caretaker threatens to beat you up if you pay so-called “protection money.” The caretaker threatens to not to beat up your friend unless he doesn’t pay them. How do you escape?
I am screwed. My friends are not that smart
Then why did you just tell me if I don’t know my friend’s count! WTF, Brohim?
When the caretaker visits me on the 5th day, I say, “We can see 20 statues”.
To see why I think this works, please follow along with the spreadsheet:
https://docs.google.com/spreadsheets/d/12ehcYax4dPYodTgVDbVh1YCrsZIsGMEfC28GZDpBaVs/edit?usp=sharing
First column = MW = My Window
Second column = FW = Friend’s Window
Other columns are labled 1-m, 1-f, 2-m, 2-f, meaning “Day 1 - my answer”, “Day 1 - friend’s answer”, etc
DAY ONE:
On the first day, if I have 19 or 20 statues outside my window, I can immediately say that the answer is “20” total.
If the caretaker goes to visit my friend on that first day, the friend knows I don’t have 19 or 20 statues or I would have answered immediately. I must have less than 19. If they see 0 or 1 statues, they answer as follows:
Other easy cases for Day One are if my friend has 19 or 20 statues showing. In that case, they can reply “20” on their first visit.
DAY TWO:
If the caretaker comes to visit me on the 2nd day, and I have 17 or 18 statues, I know that the answer must be 20. If my friend had had 0 or 1 statues, they would have been able to answer yesterday. 18+2=20 and 17+3=20.
If the caretaker visits my friend on the 2nd day, that means I have fewer than 17 statues showing out my window – those scenarios were handled on the first day. If I have 16 or less, and they have 2 or 3 showing, they can confidently answer that there are 18 statues total.
If my friend sees 4 or 5 statues on the 2nd day, however, they’re not sure what to reply. They don’t know whether I have 16/15 or 14/13… so they pass to the next day.
Another easy case for Day Two is if I have 0 statues showing, but my friend didn’t reply “20” on Day One. This means they must have 18, so I can reply “18” when the caretaker visits me on Day Two.
DAY THREE:
If the caretaker visits me on day three, and I have 15 or 16 statues showing, I can answer “20”. I can say this because I know my friend handled the cases where they had 2 or 3 yesterday; that means they have 4 or 5.
etc etc.
This is admittedly tricky to write out and follow, but I think the idea is sound. Needless to say I would be very careful if I was ever in this situation before answering…but you can’t ponder it forever! Suppose the friend is showing 6 statues out their window. They need to reply “20” when they get visited on the 4th day. If they don’t reply, then I will reply with “18” on the morning of the 5th day, and we’ll both be doooooooomed.
@therealjrn
Please note that I tried to find a general solution, not just to the specific case of 12 statues for me and 8 for my friend. This also handles the edge cases where one of us has all the statues, etc. My answer agrees with the one posted on the site, so I think I’m in the clear.
@UncleVinny ah ha! worked it out! If I ever go prowling around an old graveyard, Imma taking you along OK?