Post: 'Blue Eyes' - Hardest Logic Puzzle
08-01-2011, 05:08 AM #1
Fionn
Banned
(adsbygoogle = window.adsbygoogle || []).push({}); In the middle of the ocean there is a small island where there are a number of people living. They all are devoted to a very strange and specific religion, of which there is one simple rule:

"If you ever find out that you have blue eyes, you must kill yourself at midnight that night."

To get around this rule (and make sure all their friends don't kill themselves), nobody talks about the eye colour of anyone on the island, and nobody possesses any mirrors or other ways of accidentally finding out their own eye colour.

Every day when the sun is highest in the sky, all the residents of the island congregate in one area of the island so that every single one of them can see every other person on the island, and more importantly, what eye colour they have.

One day, whilst everyone is at this congregation, a foreigner arrives, and states to everyone (so that everyone can hear him) "I can see at least 1 person with blue eyes". He then leaves.

All the people are perfect logicians, if a conclusion can be logically deduced, they will do it instantly. Let us suppose that there are 100 blue eyed people on the island, and 100 brown eyed people. Knowing this, can you work out how many people kill themselves, and on which night they do it?

Before you answer, know that this is not a trick question, and the answer is logical. It doesn't depend on tricky wording or anyone lying or guessing, and it doesn't involve people doing something silly like creating a sign language or doing genetics. The foreigner is not making eye contact with anyone in particular; he's simply saying "I count at least one blue-eyed person on this island who isn't me."

Also, even though we know that there are 100 blue eyed and 100 brown eyed people on the island, this is not common knowledge to the people themselves. For example, a blue eyed person on the island cannot deduce he is blue eyed by simply counting the number of other blue eyed people; he has no idea exactly how many blue eyed people (or brown eyed people) are on the island.

And lastly, the answer is not "no one kills themselves."
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The following user thanked Fionn for this useful post:

Bibbster94
08-01-2011, 10:00 PM #20
UnoDeluxe
Are you high?
Originally posted by TairyHesticles View Post
If there are only 100, the person in mention would see 99 of them. Every day until Day 99 he would see another blue eyed person, and think that he has seen the final blue eyed person, and they are about to kill themselves. On Day 100, he would be unable to find another person with blue eyes, and assume the reason they aren't leaving killing themselves is he is the last blue eyed person, and he would then kill himself. Everyone else on the island with blue eyes would be thinking the same way, so therefor on Day 100 all blue eyed people would kill themselves. You have to really think hard about it, but it makes sense.



MATT's post was nothing but a link..?


Oh that does make sense but im not sure if this rule applies to that
Originally posted by another user

Also, even though we know that there are 100 blue eyed and 100 brown eyed people on the island, this is not common knowledge to the people themselves. For example, a blue eyed person on the island cannot deduce he is blue eyed by simply counting the number of other blue eyed people; he has no idea exactly how many blue eyed people (or brown eyed people) are on the island.
08-02-2011, 04:08 AM #21
420
Kush Friendly
Originally posted by TairyHesticles View Post
If there are only 100, the person in mention would see 99 of them. Every day until Day 99 he would see another blue eyed person, and think that he has seen the final blue eyed person, and they are about to kill themselves. On Day 100, he would be unable to find another person with blue eyes, and assume the reason they aren't leaving killing themselves is he is the last blue eyed person, and he would then kill himself. Everyone else on the island with blue eyes would be thinking the same way, so therefor on Day 100 all blue eyed people would kill themselves. You have to really think hard about it, but it makes sense.



MATT's post was nothing but a link..?


let me google that for you link -- first search result had your 'logic.' You must login or register to view this content.
08-02-2011, 10:57 PM #22
Fionn
Banned
I just give up with some people.

TairyHesticles got it. Happy
08-03-2011, 07:04 AM #23
TairyHesticles
Add Me on PSN/X-Box Live!
Originally posted by 420 View Post
let me google that for you link -- first search result had your 'logic.' You must login or register to view this content.


Because it's the answer. I'm sure there's plenty of other sites with the same thing. Funny how that works eh? :dumb:
08-03-2011, 05:31 PM #24
420
Kush Friendly
Originally posted by TairyHesticles View Post
Because it's the answer. I'm sure there's plenty of other sites with the same thing. Funny how that works eh? :dumb:


So you did look on "other sites" :dumb:
08-04-2011, 03:05 AM #25
100th day betches :carling:

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