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In this lesson, students will learn how to determine the greatest common factor of two numbers using two strategies: (1) listing the factors of each number and (2) determining the factors of the difference of the numbers and then choosing one of those factors as the greatest common factor (or GCF). Students will use the GCF to simplify ratios in one step.

Module 1 Video

In this video, both strategies for determining GCF are mentioned: listing the factors of both numbers and choosing a factor of the difference of the numbers.

Module 2 Video

In this video, multiple, common multiple, and least common multiple are defined with an example. There is no greatest common multiple. The method of multiplying two numbers and dividing by their GCF to get their LCM is mentioned.

You can have students raise and discuss questions about the video and allow students the opportunity to work through one or two different examples they can think of (different number pairs).