Module 3:
Greatest Common Factor (GCF)
What is GCF?
GCF stands for greatest common factor. The greatest common factor of two numbers is the greatest number that is a factor of both of the numbers.
How to find the Greatest Common Factor:
One way to find the GCF of two or more numbers is to list the factors of each number. Next, find the greatest (largest) factor they have in common.
Example 1: GCF of 6 and 18
Factors of 6: 1, 2, 3, 6
Factors of 18: 1, 2, 3, 6, 9, 18
Both 6 and 18 have many common factors BUT 6 is the greatest number that they have in common. Therefore, the GCF of 6 & 18 = 6.
Video of GCF
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What is the GCF of 45 and 36?
The factors of 45 are 1, 3, 5, 9, 15, 45.
The factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18, 36.
So the GCF of 45 and 36 is 9.
What is the GCF of 45 and 36?
The factors of 45 are 1, 3, 5, 9, 15, 45.
The factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18, 36.
So, the GCF of 45 and 36 = 9.
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What is the GCF of 48 and 56?
Factors of 48- 1-2-3-4-6-8-12-16-24-48
Factors of 56- 1-2-4-7-8-14-28-56
The GCF of 48 and 56 = 8
What is the GCF of 48 and 56?
Factors of 48 - 1, 2, 3, 6, 8, 12, 16, 24, 48
Factors of 56 - 1, 2, 4, 7, 8, 14, 28, 56
GCF of 48 and 56 = 8
Challenge ?: What is the GCF of 60 & 72?
60- 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60
72- 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72
The GCF of 60 & 72 = 12.
What is the GCF of 60 & 72?
60 - 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60
72 - 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72
The GCF of 60 & 72 = 12