 All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars  perplexus dot info  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) Comments: ( Back to comment list | You must be logged in to post comments.) Solution | Comment 86 of 89 | My Solution is there is no solution and here is why. Pythagorean theorem says that a squared + b squared = c squared.  We know 2 parts of it which is 5 and 7.  since 7 is bigger then 5, 5 can not be the hypotnuse which leaves 2 ways the problem can be done.

5(5) + 7(7)=c squared

25+49=c squared

74=c squared

or

5(5) + b squared=7(7)

25+ b squared=49

-25                  -25

b squared=24

b= not a prime number

Therefore there is no solution

 Posted by Briana on 2005-04-23 02:35:31 Please log in:

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