### GCSE Maths Revision: Factors, Common Factors & HCFs

#### 4th April 2017

Factors, Common Factors and HCFs - GCSE Maths Number Syllabus

Understanding these terms is really important. You should have encountered them during KS3 but it’s important that you revise them for your GCSEs as they are likely to come up in some shape or form. So let’s take a look at what a factor is and how to work it out.

Factor - a number that goes into another number.

Eg. 1, 2,3,  4, 6 and 12 are factors of 12.

We can work this out using the following multiplication strategy:

1 x 12

2 x 6

3 x 4

6 x 2

12 x1

All of these numbers multiply together to give 12 - that means that they are factors of 12.

Common factors - these are factors that are factors of more than one number.

Eg. factors of 12 are 1, 2, 3, 4, 6 and 12

factors of 30 are 1, 2, 3, 5, 6, 10, 15 and 30

The common factors of 12 and 30 are 1, 2, 3 and 6 - this is because they are factors of both numbers.

Highest common factors - this is the largest common factor. So let’s take the same sample as above:

factors of 12 are 1, 2, 3, 4, 6 and 12

factors of 30 are 1, 2, 3, 5, 6, 10, 15 and 30

The common factors of 12 and 30 are 1, 2, 3 and 6 - this is because they are factors of both numbers. The HCF is 6 - because it is the highest number that is a factor of both 12 and 30.

Now that you understand the basics, have a listen to our song, watch the video and test yourself using our quiz - your GCSE Maths exam won’t seem so daunting once you give it a go!

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