Monday, October 6, 2008

Prime Time?



The other story currently on the 'Numbers in the News' board is the discovery of the world's largest prime number which has over 13 million digits! (BBC story here).  A prime number can only be divided by itself and 1.  What possible use is that information I hear you cry?  Well, if it wasn't for prime numbers we wouldn't have internet security.  When you make a purchase online your details are kept secure by a process called encryption and it all relies on very large prime numbers.  S3/4 have been looking at encryption in Computing.

Many year ago an Egyptian dude called Eratosthenes found a good way of finding primes - get rid of the ones that aren't!  S1 followed in his footsteps.  In the grid above all the multiples of 2, 3, 5 and 7 are coloured red.  The numbers in white are all prime numbers.  Voila!

Mr C

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