# Questions tagged [blue-eyes]

For questions related to the puzzle of islanders who can only leave when they deduce the colour of their own eyes.

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### Alternate 100 Blue Eyed Islanders Riddle Conclusion - Contradictory Laws

In the 100 blue-eyed islanders riddle, there is a rule that if an islander figures out his eye color, he must leave the island. Doesn't that contradict the other rule that he can't inform anyone else ...
481 views

### Doesn't saying "at least 99 of you have green eyes" give new information?

The Logic Puzzle I have found a catch in the solution of this logic puzzle. Provided that you are not allowed to give the prisoners any new information, the statement "at least 99 of you have ...
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### 2 blue eyes 99 red eyes

There are 101 normal people on an island. 2 have blue eyes and the rest have red eyes. The people with red eyes can leave the island. But the people with red eyes always tell the truth and the people ...
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### Blue eyes riddle: a counter-argument to accepted solution

I would like help understanding my flawed logic in my following reasoning: The Blue-eyes Riddle is commonly expressed as A group of people with assorted eye colors live on an island. They are all ...
2k views

### Disaster on Blue-Eyes Island

A particular island has 100 inhabitants. None of them know their own eye colour. They are all perfect logicians. Every night at midnight, a ferry stops on the island, and every islander who has ...
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### Variant of blue eyes puzzle [closed]

There are a total of 200 players assigned to either A or B at a certain venue. There are actually 100 of each, but the players don't know that. They don't know which one they are. Of course, there is ...
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### 100 blue-eyed people riddle N=4

The solution of this riddle is usually given with explicit reasoning for two cases: Case where there is only 1 blue-eyed person, Case where there are 2 blue-eyed people. That logic is clear, and I ...
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### Blue eyes riddle: why do all nested hypotheses need to be considered?

Note: This is the second try at asking something that has not yet been answered by the excellent answers to the Oracle question or the skip-ahead question. In this answer to my previous attempt at ...
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### Blue eyes riddle: what information is gleaned after the first night?

There are good explanations on this site and xkcd of the inductive reasoning leading to the riddle’s solution, but nowhere have I found an answer to the following aspect: Exactly what information is ...
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1 vote
265 views

### Mensa 3rd Grade Recess Game [closed]

Mensa 3rd Graders At Recess There are dozens of variations of this puzzle type, but I put my own spin and characteristics to it. It is lunch time for the little ones at Mensa Mini's Private School. ...
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### A false and a true statement in the blue-eyed puzzle

Here is a variant on the blue-eyed puzzle. I hope it brings at least some more difficulty than the original one, even if you know the solution to the original. The Guru makes the following statement: ...
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### Faster Solution for Blue-eyed Monks [closed]

A little history - I read about a blue-spotted monk version of this problem on another site. A "better" solution came to me, which I posted on my blog (theSilentKnight.info). A couple of people ...
118 views

### About the 100 blue eyes problem [duplicate]

I thought I understood your answer and liked it, but just read a different explanation at http://thesilentknight.info/2016/flawed-logic-blue-spot-problem/ that suggests that the 100 people would all ...
4k views

### The origin of the blue eyes puzzle

The Blue Eyes puzzle is possibly the most popular induction-based puzzle known. Is it really known who was the first to come up with it (in any form). The link at xkcd says: I didn't come up with ...
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### Mixed Up Memberships

In a small town, there exist a number of organizations of people. Each year, they send out a list of their members to everyone and this is the official way in which people know they are part of an ...
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### Exponential time in a Blue Eyes variant

I created a variant of the Blue Eyes problem where the logic took 4901 days (over 13 years) to totally play out. I thought this was nice, but I was hoping for an even longer period of time. Of ...
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### Numbered Logicians near the Blue Eyes island

There is an island near the famous Blue Eyes island where 100 perfect logicians live, each with a number between 1 and 100 (repetitions allowed) tattooed on their forehead. They know all the numbers ...
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### The Dot-town suicide

Each resident of Dot-town carries a red or blue dot on his (or her) forehead, but if he ever figures out what color it is he kills himself. Each day the residents gather; one day a stranger comes and ...
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### Variant to blue eyes puzzle - selfish logicians

This is a variation of the blue eyes puzzle. Suppose the logicians want to get off the island. They are selfish and think only of themselves. They may help others as well, but solely for their own ...
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### Another twist on the blue-eyed puzzle

In Variants to blue eyes puzzle we explored what would have happened if the oracle of the Blue Eyes puzzle had said something different with different numbers of islanders. I've got another one for ...
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### Variants to blue eyes puzzle

Here are some variants to the Blue Eyes puzzle. All the rules are the same, but there are differences in (a) the number of people of different eye colors and (b) the oracle's statement. It is not ...
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### Green Eyed Oracle Variant - Not a Multiple of 17

100 perfect logicians have been gathered on an island. It is common knowledge that logicians always have blue or brown eyes, though on this island, all eyes are blue. However, there are no reflective ...
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### In the blue-eyes puzzle, why can't they skip ahead? [duplicate]

In the solution to the Blue Eyes logic puzzle, there is a follow-up question: Each person knows, from the beginning, that there are no less than 99 blue-eyed people on the island. How, then, is ...
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