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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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 No Subject | Comment 60 of 89 |
the number must be five also. "1" is not properly called prime, and 7+5=12 therefore, the prime number must be less than 12. I deduce that it is 5 because it is the only one that equals a prime number (17). however 11 also works but who's to say it's a double digit? you're question is too vague.
 Posted by rachael on 2005-03-18 02:56:18

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