How do you calculate the Greatest Common Factor?

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If you need to find the GCF for two numbers , follow the following steps:

1. Factor the numbers to its prime factors.

2. multiply the common primes.

Example:

Find the GCF for 36 and 54.

1. Factor both numbers.

36 = **2***2***3*****3**

54= **2***3***3*****3**

Now we will multiply the common factors (in bold line).

==> GCF = 2 * 3*3 = 18

Then, the greatest common factor is 18.

Example (2);

Find the GCF for 48 and 64.

1. Factor both numbers.

==> 48= 2*2*2*2*3

==> 64 = 2*2*2*2*2*2

2. Choose common primes and multiply.

==> GCF = 2*2*2*2= 16

You find the biggest common number 2 numbers can be divided by.

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