Finding GCF by Listing Factors
The Greatest Common Factor (GCF) of two or more numbers is found by listing all factors of each number, identifying the factors that appear in every list, and selecting the largest one. For 12 and 18: factors of 12 are 1, 2, 3, 4, 6, 12; factors of 18 are 1, 2, 3, 6, 9, 18; common factors are 1, 2, 3, 6; GCF = 6. This foundational skill from Reveal Math, Course 1, Module 5 is required for factoring expressions, simplifying fractions, and solving word problems involving equal groups in 6th grade math.
Key Concepts
To find the Greatest Common Factor ($\text{GCF}$) of two or more numbers by listing: 1. List all the factors of each number. 2. Identify the common factors shared by all the numbers. 3. Identify the greatest number from the list of common factors.
Common Questions
How do I find the GCF by listing factors?
List all factors of each number from least to greatest. Identify factors that appear in all lists. The largest shared factor is the GCF.
What is the GCF of 12 and 18?
Factors of 12: 1, 2, 3, 4, 6, 12. Factors of 18: 1, 2, 3, 6, 9, 18. Common factors: 1, 2, 3, 6. GCF = 6.
What is the GCF of 15 and 25?
Factors of 15: 1, 3, 5, 15. Factors of 25: 1, 5, 25. Common factors: 1, 5. GCF = 5.
What is the GCF of 8, 16, and 20?
Factors of 8: 1, 2, 4, 8. Factors of 16: 1, 2, 4, 8, 16. Factors of 20: 1, 2, 4, 5, 10, 20. Common factors: 1, 2, 4. GCF = 4.
Why is the GCF important in 6th grade math?
The GCF is used to factor expressions, simplify fractions to lowest terms, and solve word problems that involve splitting things into equal groups.
When do 6th graders learn to find the GCF?
Module 5 of Reveal Math, Course 1 covers GCF in the Numerical and Algebraic Expressions unit.