Jump to content
BrainDen.com - Brain Teasers
  • 0

All primes



4 answers to this question

Recommended Posts

  • 1

Given that the ages are primes, at least two of the ages must be odd. The difference of any two odd numbers must be even, and as the difference is given to be prime that difference must be 2 -- the only even prime. As the ages must be different (as zero is not prime), it can be deduced that one and only one of the ages must be even, id est 2.  The set of ages must then be {2, p, p+2}, such that p is a prime and p-2 and p+2 are also prime. This only occurs where p is equal to 5: (p-2) = 3 & (p+2) = 7. It therefore can be declared the set of ages is {2, 5, 7}.


Edited by DejMar
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Create New...