Puzzle 1: P is prime...

Discussion in 'Math' started by Dave, May 31, 2009.

  1. Dave

    Thread Starter Retired Moderator

    Nov 17, 2003
    6,960
    144
    I've not done this for a while so when I came across a couple of puzzles I immediately thought of you guys! I wasn't sure where to post this, but having looked at the puzzles these are very much mathematically focused so thought that the Math forum was the best place.

    Ok, so puzzle 1:

    Why is that if p is a prime number bigger than 3, then p^2-1 is always divisible by 24 with no remainder?

    Dave
     
  2. Ratch

    New Member

    Mar 20, 2007
    1,068
    3
    Dave,

    This guy explains it as good as anyone can.

    http://puzzles.nigelcoldwell.co.uk/fifteen.htm

    Ratch
     
  3. Dave

    Thread Starter Retired Moderator

    Nov 17, 2003
    6,960
    144
    I know Nigel well; in fact many of the puzzles I am looking at are collated on his site.

    For anyone wanting to attempt this puzzle (and other puzzles), don't go onto the above link (or Nigel's site) as it contains the answer(s). I will use Nigel's site for the actual answers when people have had a chance to do the puzzles.

    Dave
     
    Last edited: May 31, 2009
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