How to Find the GCF and LCM of 3 Numbers Using Prime Factorization | Math with Mr. J
From Math with Mr. J
14 min6thMath
Summary
How to find the greatest common factor (GCF) and least common multiple (LCM) of two numbers. Mr. J shows listing and prime-factorization methods and when each is useful.
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Teaching resources
Discussion questions
The GCF is the biggest factor two numbers share; the LCM is the smallest multiple they share.
- What is the difference between a factor and a multiple?
- How is the GCF useful for simplifying fractions?
- How is the LCM useful for adding unlike fractions?
Quick work-a-long
Words to know: factor, multiple, GCF, LCM
- Find the GCF of 12 and 18.
- Find the LCM of 4 and 6.