# Grade 8 Math: 1.3 Common Factors and Common Multiples

This lesson goes through how to find the greatest common factor (GCF)--also known as the highest common factor (HCF)--and least common multiple (LCM) of two numbers. It starts off with an example of calculating it using the technique in section 1.1, but then moves on to show that the GCF and LCM can be calculated much more efficiently using prime factorization and Venn diagrams.

Watch out for two common misunderstandings: (1) Confusing factors with multiples and (2) Forgetting to find only prime factors for a number when using prime factorization.

The final example shows students how to calculate the GCF and LCM in the quickest way possible, by using a factor tree then a Venn diagram.

Here are the notes in PDF format: 2014-08-30 1.3 Common Factors and Common Multiples.pdf

VIDEO: For a video explanation of the process, please refer to this link.

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