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 Prime Perimeter (Posted on 2005-03-11)

You and two other people have numbers written on your foreheads. You are all told that the three numbers are primes and that they form the sides of a triangle with a prime perimeter. You see 5 and 7 on the other two heads and both of the other people agree that they cannot deduce the number on their own foreheads.

 See The Solution Submitted by Erik O. Rating: 2.8235 (17 votes)

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 re(2): centering the point | Comment 53 of 89 |
(In reply to re: centering the point by pcbouhid)

Pcbouid:

As I said before I think that your solution is fine. Let me say that I think it is complet in order at the problem post.

I ment only in my mail that we have assumed that 11 is a solution to the problem, proceeding by way of exclusion: the other numbers couldn't be, it is stated that there is a solution, so the only number that remains is the solution.

But we haven't verify that 11 is a solution, appliying to 11 the same approach used to the other primes. Sure: we are not obliged to, but can be done...

It was only this. It's not important. Armando.

 Posted by armando on 2005-03-14 21:46:09

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