Primes

Tuesday 27th April (TERM 2).

The class had a go at a number puzzle called KENKEN



Next we were watching a youtube video of the **prime factorization** of 72. This was revision from last term media type="youtube" key="3VflanaZ1Qc" height="264" width="324" And then some "prime number hockey" media type="youtube" key="bXy8_i3M3UA" height="344" width="425"

**WHAT IS A PRIME?**
Then we got into groups and tried to explain what the rules of "prime hockey" were.

media type="youtube" key="_VI9u5Qf4kU" height="344" width="425": Above is a youtube video which counts out the first sixty prime numbers in sixty seconds with some nice imagery in the background

Mr Radonich showed us some activities he has added to the website that he said we needed to do for homework. The [|"Pumpkin Multiples"] Activity and an exercise on primes from the orange Alpha homework books.

Here is a table of division that might be useful to you when trying to find out if a number is prime. Divisibility Rules! To find if some number X is divisible by a certain number, test the number by using the information in the table below. i got this information off this site:http://www.lifesmith.com/mathfun.html some of the biggest primes: Primes! As of 2003, the largest known prime number has been verified as 2^13466917 - 1. Known as the 39th Mersenne prime number, that is, of the form 2^p - 1, where p is also prime, it has 4,053,946 whopping digits! You can see it [|HERE]! In February, 2005, an even larger Mersenne prime was found! Yes, believe it or not, the 42nd Mersenne prime was independently verified as 2^25,964,951-1, an astounding number having 7,816,230 incredible digits...there is a poster available of it too...I'll have to find where...
 * By 2 || If the last digit divisible by two, then X is too ||
 * By 3 || If the sum of the digits of the number X is divisible by three, then X is too ||
 * By 4 || If the last two digits are divisible by four, then X is too ||
 * By 5 || If the last digit is 5 or 0, then X is divisible by 5 ||
 * By 6 || If X is divisible by 2 and by 3, then X is divisible by 6 ||
 * By 7 || This rule is called L-2M. What you do is to double the last digit of the number X and subtract it from X without its last digit. For instance, if the number X you are testing is345678, you would subtract 16 from 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by seven. Then the X's divisibility will be the same. ||
 * By 8 || If the last three digits are divisible by 8, then X is too ||
 * By 9 || If the sum of the digits of the number X is divisible by nine, then X is too ||
 * By 10 || If the last digit of X is 0, then X is divisible by 10 ||
 * By 11 || What you do here is to make two sums of digits and subtract them. The first sum is the sum of the first, third, fifth, seventh, etc. digits and the other sum is the sum of the second, fourth, sixth, eighth, etc. digits. If, when you subtract the sums from each other, the difference is divisible by 11, then the number X is too ||
 * By 12 || If X is divisible by 4 and by 3, then X is divisible by 12 ||
 * By 13 || This rule is called L+4M. What you do is to quadruple the last digit of the number X and add it from X without its last digit. For instance, if the number X you are testing is345678, you would add 32 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by thirteen. Then the X's divisibility will be the same. ||
 * By 14 || If X is divisible by 7 and by 2, then X is divisible by 14 ||
 * By 15 || If X is divisible by 5 and by 3, then X is divisible by 15 ||
 * By 16 || If the last four digits are divisible by 16, then X is too ||
 * By 17* || This rule is called L-5M. See rules for 7 and 13 on how to apply. ||
 * By 18 || If X is divisible by 9 and by 2, then X is divisible by 18 ||
 * By 19* || This rule is called L+2M. See rules for 7 and 13 on how to apply. ||
 * By 20 || If X is divisible by 5 and by 4, then X is divisible by 20 ||
 * By 21 || If X is divisible by 7 and by 3, then X is divisible by 21 ||
 * By 22 || If X is divisible by 11 and by 2, then X is divisible by 22 ||
 * By 24 || If X is divisible by 8 and by 3, then X is divisible by 24 ||
 * By 25 || If the last two digits of X are divisible by 25, then X is too ||
 * Higher || You can use multiple rules for multiple divisors...for instance, to check if a number is divisible by 57, check to see if it is divisible by 19 and 3, etc., since 57 = 19 x 3... ||