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Sep 072013
 

Have a go at this worksheet to find all the Prime Numbers less than 100.

eratostenes

 

Now try this much bigger Sieve to find all the Prime Numbers less than 400! Start by clicking on 2 and all the multiples of 2 will be removed. Then click on 3 to remove the multiples of 3 and continue clicking on the prime numbers until you are only left with red prime numbers.

Also take a look at this video

Apr 172013
 

Here is a great starter from Transum

http://www.transum.org/Software/SW/Starter_of_the_day/starter_April14.asp

Mar 022013
 

Here are two clear examples showing how to find the prime factors of a number.

Oct 302011
 

A factor is a number that divides into another number without a remainder. So the factors of 15 are 1, 3, 5 and 15.

The multiples of 4 are all the numbers in the 4 times table. 4,8,12,16,20,24,28,32……..

A prime number is special because it only has 2 factors.  These two factors are always 1 and the number itself. So 7 is a prime number because the factors of 7 are 1 and 7.

Try matching the questions to the answers in these columns.