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Surf City Semiprimes (Posted on 2011-09-27) Difficulty: 2 of 5

Let n be some arbitrarily huge number; call each prime between 1 and n a 'GIRL'; call each even semiprime between 1 and n a 'BOY'.

Prove that there are two GIRLs for every BOY.

(An even semiprime is a composite number one of whose two prime factors is 2.)

See The Solution Submitted by broll    
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Some Thoughts Menage a trois | Comment 1 of 4
Is this supposed to be exact, or approximate?

It does not hold exactly for n = 6 (admittedly not a huge number), so I suspect that it does not hold exactly for all huge numbers.

For n = 6, there are 3 girls (2, 3 and 5) and 2 boys (4,6).

In fact, it obviously cannot be true whenever the number of GIRLs is odd, which I suspect is the case for approximately half of all arbitrarily huge n.


  Posted by Steve Herman on 2011-09-27 10:38:32
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