## GREATEST COMMON FACTOR

### What is the highest common factor

HCF is also called GCD - Greatest Common Divisor - or
GCM - Greatest Common Measure or GCF - Greatest Common Factor.

The best way to find the greatest common factor is to keep
finding the factors of the smaller number, starting from
the largest factor. The first factor of the smaller number
that is also a factor of the larger number is the highest common factor.

It is easier to understand how to find the greatest common factor when
using an example

What is the greatest common divisor of 12 and 20?
The largest factor of 12 is 12, but 12 is not a factor of 20.

The next factor is 6, but 6 is not a factor of 20.

The next factor is 4, and yes 4 is a factor of 20.
So now you have find the greatest common factor.

### Greatest common factor division method

Using the division method is another way to find the
greatest common divisor.

Example to find the greatest common factor of 180 and 30.

108= 30 x 3 + 18

30 = 18 x 1 + 12

18 = 12 x 1 + 6

12 = 6 x 2 + 0