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The Lever: A Logic Problem


Chaos Pudding

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Guest Chaos Pudding

A prison (I know, how original, right?) is overfilled with prisoners. The warden decides to give the prisoners a chance to earn their freedom. He gathers them all up in a big room, and tells them that there is a small room somewhere in the prison that only has a lever in it. There is nothing else in the room. The lever can either be in the UP position or the DOWN position. The warden tells the prisoners that he will randomly pick prisoners to go to the room. While they are in there, they can chose to move the lever or not. The warden then tells the prisoners that if they claim that every prisoner has entered the room at least once and are correct (the warden keeps track), then he will set them all free. If they are incorrect, they will all die.

 

The prisoners will be in solitary confinement after this meeting, and will not see any of the other prisoners, or otherwise be able to communicate with the prisoners outside of the information given by the lever (being UP or DOWN). Devise a strategy that insures, to the highest probability, that each prisoner would have entered the room at least once before contacting the warden. This problem can be solved both if the prisoners are told what position (UP or DOWN) the lever is in before anyone enters the room, and if they are not told.

 

I will give 1 Rep to the first person who posts a working strategy for the known lever position, and 2 Reps to the first person who posts a working strategy for the unknown position.

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Everyone take off a piece of clothing (A slipper?), and put in the corner of the room.

 

Make it noticible if you're first, that way the next prisoner will instantly know what to do.

If every prisoner knows exactly how many prisoners there are in total, the last prisoner (Every one will end up counting anyway) simply counts the slippers.

lf there is 1, just 1 less (Including your own slipper), not everyone entered.

The lever, to me, is a diversion.

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Guest Chaos Pudding

Everyone take off a piece of clothing (A slipper?)' date=' and put in the corner of the room.

 

Make it noticible if you're first, that way the next prisoner will instantly know what to do.

If every prisoner knows exactly how many prisoners there are in total, the last prisoner (Every one will end up counting anyway) simply counts the slippers.

lf there is 1, just 1 less (Including your own slipper), not everyone entered.

The lever, to me, is a diversion.

[/quote']

 

Can't do that. Only way of communication is through the lever, specifically the position of said lever.

 

And as for everyone else: yes, the prisoners know how many of them there are. You, on the other hand, do not need to know.

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So everyone knows then?

If there are... 100 prisoners, hypothetically speaking.

Everyone is told the lever is DOWN. Everyone assumes to themselves that they must push the lever.

If everyone pushes it.. lt should be in DOWN position.

If it is UP, not everyone entered.

Even if it's DOWN, there's still a max 50% that not everyone pushed it.

 

Using this logic it's impossible to have a correct answer, really.(Because if 98 people pushed it, it would still be DOWN right?)

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Guest Chaos Pudding

So everyone knows then?

If there are... 100 prisoners' date=' hypothetically speaking.

Everyone is told the lever is DOWN. Everyone assumes to themselves that they must push the lever.

If everyone pushes it.. lt should be in DOWN position.

If it is UP, not everyone entered.

Even if it's DOWN, there's still a max 50% that not everyone pushed it.

 

Using this logic it's impossible to have a correct answer, really.(Because if 98 people pushed it, it would still be DOWN right?)

[/quote']

 

You're doing it so horribly wrong. -_-

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Guest Chaos Pudding

Explain how.

 

Well, for one, it isn't impossible. I've thought up at least 1 way that works 100% of the time if you know the lever, and 99.999...% of the time (depending on how much time you want to give) for not knowing the lever.

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Oh fudge sticks, I've seen this riddle before. <_<

 

"At least once..." meaning they can enter the room more than once.

 

This is just my bullshit answer without thinking, but if it's their first time in the room they move the level so that's it up, and if it's there second (or subsequent) time they move it so that it's down.

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I've seen something similar to this that involved school kids and a light bulb. =\ I don't remember the answer though. :(

 

But to help anyone wondering, you don't need to know the amount of people, there's nothing special about the lever. There's a way you can do it with little to no information if I remember correctly.

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Guest Chaos Pudding

"If you know the lever..."

... So it's not an ordinary lever?

 

And it's not exactly easy since l don't even know how many prisoners there are >_>

No matter how insignifigant that is to the answer' date=' l still need a number. That's how l work.

[/quote']

 

It's an ordinary lever. It doesn't do anything except be in the UP position or the DOWN position.

 

You don't need to know how many prisoners there are. It's like asking if one of the prisoners has blue hair. It isn't needed to figure out the strategy.

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OH OH OH I THINK I GOT IT.

 

Up corresponds to an even number people left to be in the room for the first time.

Down corresponds to an odd number people left to be in the room for the first time.

 

Or vice versa, depending on the starting position of the lever.

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You don't know how many people there are.

 

Chaos Pudding' date=' does the warden choose which people go in?

[/quote']

 

Yah, warden chooses randomly. lrn2read

 

Srsly' date=' the prisoners need to have a discussion. l have a solution, l think...

[/quote']

 

The prisoners can make a plan before going into solitary confinement. lrn2read

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