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Can you solve the famously difficult green-eyed logic puzzle? - Alex Gendler

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One hundred green-eyed logicians have been imprisoned on an island by a mad dictator. Their only hope for freedom lies in the answer to one famously difficult logic puzzle. Can you solve it? Alex Gendler walks us through this green-eyed riddle.

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Meet The Creators

  • Educator Alex Gendler
  • Director Outis
  • Narrator Addison Anderson
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by TED-Ed

Can you think of some real-life situations where our second-order knowledge and third-order knowledge about what others know makes an important difference?

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Avatar for Aditya Pasbola
Lesson completed

yes actually we can think of them in daily life


Avatar for veronica Pinales
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Rumors start spreading about a specific person and you really don’t know who’s the right one


Avatar for Carlee Collison
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If 6 teams are in a basketball tournament and they claim they will win, who actually won?


Avatar for Sloane Taylor
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If ten people think they have the golden ticket, who actually has it?


Avatar for Hikaru Tamashiro
Lesson completed

When trying to see which person is lying to you and which one isn't.


Avatar for Dorian Marié
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Where there is a secret, you are in a group of 10 people for instance, and people can leave the room only when they are sure they know the secret, e.g.: "it's time to eat". Except that they are not sure if everybody knows the secret.

But then one person comes in and say "Oh John you look hungry". But everybody is forbidden to talk about food.

Then food trucks come by, and everytime a food truck comes by they can all go to the food truck but they have to be sure everybody wants to eat too.

:D (That was fun)


Avatar for Cristian Reyes
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in response to Scott Cleveland Show comment

All of them only if they are different kind of winning tickets


Avatar for David Li
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in response to Daniël Petri Show comment

Not sure how good of an example this was but it was pretty funny.


Avatar for Jonathan Bush
Lesson completed

Success in playing chess is not always based solely on reading the board. Sometimes you gain useful information from reading your opponent's emotions. I once read a story about a game Fischer played where his opponent laid a trap in the opening. Fischer was about to walk into the trap, but then noticed his opponent was unusually quiet and withdrawn. This raised his suspicions, and he looked at the position more deeply, thereby discovering the trap. Of course other, more interactive, games such as Poker display this feature more prominently.


Avatar for Mikael Macial
Lesson in progress

in response to Anthony Falez Show comment

Then you have to predict your enemy's action, knowing he knows what would probaly be your first movement. At the end, it seems more like luck than predicting your enemy's thoughts..

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