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Topic: Brainteaser n
Replies: 15   Last Post: Aug 6, 2003 7:10 AM

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William Hart

Posts: 28
Registered: 12/13/04
Re: Brainteaser n
Posted: Jan 13, 2003 11:39 PM
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For those who are interested, here is a brainteaser that took me more than
15 mins to solve (apologies to those who don't think it belongs here, and
to the person I pinched it from)

On the Isle of Reason live exactly 50 logicians. There are no other
inhabitants. Each day they all meet to discuss riddles and life. However
there is one topic they do not discuss. On each of their foreheads is a
blue dot. However it is so shameful to have a blue dot, that knowing this
fact for a certainty, will certainly result in the bearers' suicide the
next morning. For this reason blue dots and related things are NEVER
discussed. Fortunately there are no mirrors or reflections on the island
and so everyone is blissfully unaware of the blue dot they have, but can
see the other 49 blue dots....until, one day a visitor to the island comes
and knowing something of the strange problems of the island thinks he will
be tactful and announces "I happen to have noticed that at least one of you
has a blue dot on his forehead". He leaves the island unaware of what
follows. Precisely fifty nights pass and on the next morning all fifty
logicians commit suicide. Why?

Note: there is sufficient information in the riddle, it is not a play on
words and can be solved by pure logic. The fact that they discuss riddles
is irrelevant. They could come together each day without a word being

Finally, for those who have heard the riddle, answer this. Why does someone
need to come to the island and say that there is a blue dot? Surely each of
them can see 49 other dots and knows that there is a blue dot? The answer
must be as tight as the answer to the riddle!


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