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How to find the highest common factor

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Middle School Math

Using a factor tree to find the highest common factor

Keywords: HCF  | | Lowest common multiple |  GCF
| Math| Greatest Common Factor
The highest common factor ( HCF) is the largest number that will divide exactly into two or more numbers.

You can find the HCF by creating a factor tree for each number and look for common numbers on each factor tree.

Find the highest common factor of 9 and 27

When you create a factor tree for 9 you get the prime numbers 
3   3












factor tree for 9

With 27 you get the prime numbers 3 3 3 after creating a factor tree.
factor tree for 27
9 = 3  3

27 = 3 3 3

Notice that you have 3 and 3 on both list.
In order to find the HCF  you multiply 3 times 3 which equals 9

This process works for two or more numbers also.

The video works several examples.