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Aside from the point of the thread — do they know that there are exactly 100 of each type? If so I do not understand why they could not count all others’ eyes (without any communication) and leave all together in the first night
No, they don't know if it's 100/100 or 101/99. That's an important detail which got cropped from the tweet...
If any form of communication forbidden? Like – a 3rd person is able to recognize that 2 people have different eye colors and can separate them into groups.
Yes, that's forbidden.
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