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Lesson 4.2 Greatest Common Factor . Essential Question: How do you find the greatest common factor of two or more numbers?. Before we start…. What does it mean to have something in common? What do the numbers 4 and 8 have in common?. What is a factor?.
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Lesson 4.2Greatest Common Factor Essential Question: How do you find the greatest common factor of two or more numbers?
Before we start… What does it mean to have something in common? What do the numbers 4 and 8 have in common?
What is a factor? • Remember a factor is any whole number that can be divided exactly into another number. • 1, 2, 3, and 6 are factors of 6.
What is a common factor? • A common factor is a whole number that is a factor of two or more nonzero whole numbers. • 3 is a common factor of 3, 6, 9 and 12.
What is the greatest common factor (GCF)? • The greatest common factor (GCF) is the greatest of the common factors. • It’s the highest number factor that appears in each number’s factor list. • 12 has the factors: 1, 2, 3, 4, 6 and 12. • 16 has the factors: 1, 2, 4, 8 and 16. • The GCF of 12 and 16 would be 4.
How do you find a GCF? • Make a list of all the factors and identify the greatest number on each list. • Write the prime factorization of each number. • Find the common prime factors. • Multiply the factors. Your product is the GCF.
What if there isn’t any GCF? • Sometimes you’ll have numbers that won’t have any factor in common other than 1. • Two numbers are relatively prime if their greatest common factor is 1. • 8 and 15 are relatively prime.
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How do you find the greatest common factor of two or more numbers?
Ticket Out the Door Find the greatest common factor of 16 and 28