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.
What is the number written on your forehead?
(In reply to
re: A solution to Pat by pcbouhid)
on another note, if I have a 5 on my head, the other guy with a 5 is
seeing exactly what we are. This implies that he can solve it, it's not
solveable, or you are wrong pat. I am saying you are wrong...
If he sees the 7 + 5, he's seeing exactly what we see. This means that
he has the same problem as us. Now, under that assumption, you would
have to say that if he can solve it, the equation doesn't work. You
would also have to say that if he cannot solve it, which is what they
say, if they cannot solve it with the same information as us, then we
cannot solve it.
By these definitions, the number cannot be seven or five, because if I
have a 7, the person with the 7 sees a total of 12 along with me, and
if i have a 5 the person with 5 sees the same as me. No other person
can be seeing the same as I or the equation doesn't work because then
we can't solve it, or everyone can, makeing those #'s not fit the
equation.

Posted by jon
on 20050408 23:28:55 