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Sep 072013

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



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

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.