Re:Blue Eyes Logic Puzzle
by Mindless2112 on Friday January 03, 2014 @02:42PM
(#7007615)
It is not necessary for the blue-eyed people to know the total number of blue-eyed people in the tribe, they can deduce it at day 100:
* A blue-eyed person observes 99 blue-eyed people.
* On day 99, the blue-eyed people do not commit ritual
suicide.
* Thus each blue-eyed person learns that all the blue-eyed
people also observe 99 blue-eyed people.
* Thus the blue-eyed person knows that the other blue-eyed
people must observe that he/she has blue eyes.
Re:Blue Eyes Logic Puzzle
by benjohnson on Friday January 03, 2014 @02:47PM
(#7007651)
>> The fact that the tribe still existed means, they didn't know the totals.
That's the crux of it right there.
If I may also add: the outside observers remark didn't tell the tribe any information they didn't already know - that there is a blue-eyed tribe member.
If they knew the color counts, they would know their eye color and all would have to commit suicide. The fact that the tribe still existed means, they didn't know the totals.
For example, if I know there are 100 people with blue eyes and I can count as many without including myself, then I must have brown eyes and must kill myself.
So again, there is no possible way the tribe had any idea what the exact counts where.
As a brown eyed person, there are either 100 blue eyed people meaning I have brown eyes, or there are a 101 blue eyed people and I have blue eyes. If a census was ever taken and the exact number known everyone would have to commit suicide.
Since the visitor didn't mention an exact number then there is still no way to know if you have blue or brown eyes.
However, the tribe now knows that the visitor knows he himself has blue eyes. Will they make him follow their ritual?
Update: OK, after reading the link in the first comment, I get it.