Greatest Common Factor

Greatest Common Factor - Transcript

Greatest Common Factor
Lesson 3 3

Greatest Common Factor GCF
The greatest common factor is the largest factor that two numbers share Let s find the GCF of 12 and 42 First we need to make a list of factors for each number

12 1 x 12 2x6 3x4 4x3

42 1 x 42 Factors of 12 2 x 21 3 x 14 1 2 3 4 6 12 4 x Factors of 42 5 x 1 2 3 6 7 14 21 6 x 7 7x6 42

Common Factors 1 2 3 6 Greatest Common Factor 6

What is the GCF of 18 and 27
18 1 x 18 2x9 3x6 4x 5x 6x3 Factors of 18 1 2 3 6 9 18 Factors of 27 1 3 9 27 Common Factors 1 3 9 GCF 9 27 1 x 27 2x 3x9 4x 5x 6x 7x 8x 9x3

What is the GCF of 48 and 60
48 1 x 48 2 x 24 3 x 16 4 x 12 6x8 60 1 x 60 2 x 30 3 x 20 4 x 15 5 x 12 6 x 10 Factors of 48 1 2 3 4 6 8 12 16 24 48 Factors of 60 1 2 3 4 5 6 10 12 15 20 30 60

Common Factors 1 2 3 4 6 12 GCF 12

Using Prime Factorization
Find the prime factorization of each number Identify the common factors and multiply them

Example GCF of 27 and 36
27 3x9 3x3 Ans 3x3x3 36 2 x 18 2x9 3x3 Ans 2x2x3x3
Both prime factorizations have 3x3 in common Therefore the GCF is 9

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