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**Factors and Prime Factorization**

4-2 Factors and Prime Factorization Course 1 Warm Up Problem of the Day Lesson Presentation

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization Warm Up Identify each number as prime or composite. prime composite composite composite prime composite

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization Problem of the Day At the first train stop, 7 people disembarked. At the second stop, 8 people disembarked. At the fourth stop the last 6 people disembarked. If there were 28 people on the train before the first stop, how many people left at the third stop? 7 people left at the third stop

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization Learn to write prime factorizations of composite numbers.

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**Insert Lesson Title Here**

Course 1 4-2 Factors and Prime Factorization Insert Lesson Title Here Vocabulary factor prime factorization

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**2 3 = 6 6 ÷ 3 = 2 6 ÷ 2 = 3 4-2 Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization Whole numbers that are multiplied to find a product are called factors of that product. A number is divisible by its factors. 2 3 = 6 6 ÷ 3 = 2 6 is divisible by 3 and 2. 6 ÷ 2 = 3 Factors Product

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization Helpful Hint When the pairs of factors begin to repeat, then you have found all of the factors of the number you are factoring.

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**Additional Example 1A: Finding Factors**

Course 1 4-2 Factors and Prime Factorization Additional Example 1A: Finding Factors List all factors of 16. Begin listing factors in pairs. 16 = 1 • 16 1 is a factor. 16 = 2 • 8 2 is a factor. 3 is not a factor. 16 = 4 • 4 4 is a factor. 5 is not a factor. 6 is not a factor. 7 is not a factor. 16 = 8 • 2 8 and 2 have already been listed so stop here. 1 2 4 4 8 16 You can draw a diagram to illustrate the factor pairs. The factors of 16 are 1, 2, 4, 8, and 16.

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**Additional Example 1B: Finding Factors**

Course 1 4-2 Factors and Prime Factorization Additional Example 1B: Finding Factors List all factors of 19. Begin listing all factors in pairs. 19 = 1 • 19 19 is not divisible by any other whole number. The factors of 19 are 1 and 19.

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization Check It Out: Example 1A List all factors of 12. Begin listing factors in pairs. 12 = 1 • 12 1 is a factor. 12 = 2 • 6 2 is a factor. 12 = 3 • 4 3 is a factor. 12 = 4 • 3 4 and 3 have already been listed so stop here. 1 2 3 4 6 12 You can draw a diagram to illustrate the factor pairs. The factors of 12 are 1, 2, 3, 4, 6, and 12

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization Check It Out: Example 1B List all factors of 11. Begin listing all factors in pairs. 11 = 1 • 11 11 is not divisible by any other whole number. The factors of 11 are 1 and 11.

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization You can use factors to write a number in different ways. Factorization of 12 Notice that these factors are all prime. 1 • 12 2 • 6 3 • 4 3 • 2 • 2 The prime factorization of a number is the number written as the product of its prime factors.

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization Helpful Hint You can use exponents to write prime factorizations. Remember that an exponent tells you how many times the base is a factor.

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**Additional Example 2A: Writing Prime Factorizations**

Course 1 4-2 Factors and Prime Factorization Additional Example 2A: Writing Prime Factorizations Write the prime factorization of 24. Method 1: Use a factor tree. Choose any two factors of 24 to begin. Keep finding factors until each branch ends at a prime factor. 24 24 • 6 • 2 12 4 2 • 6 3 • 2 2 • 2 2 • 3 24 = 3 • 2 • 2 • 2 24 = 2 • 2 • 2 • 3 The prime factorization of 24 is 2 • 2 • 2 • 3, or 23 • 3.

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**Additional Example 2B: Writing Prime Factorizations**

Course 1 4-2 Factors and Prime Factorization Additional Example 2B: Writing Prime Factorizations Write the prime factorization of 45. Method 2: Use a ladder diagram. Choose a prime factor of 45 to begin. Keep dividing by prime factors until the quotient is 1. 3 45 5 45 3 15 3 9 5 5 3 3 1 1 45 = 3 • 3 • 5 45 = 5 • 3 • 3 The prime factorization of 45 is 3 • 3 • 5 or 32 • 5 .

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization In Example 2, notice that the prime factors may be written in a different order, but they are still the same factors. Except for changes in the order, there is only one way to write the prime factorization of a number.

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization Check It Out: Example 2A Write the prime factorization of 28. Method 1: Use a factor tree. Choose any two factors of 28 to begin. Keep finding factors until each branch ends at a prime factor. 28 28 2 • 14 7 • 4 2 • 7 2 • 2 28 = 2 • 2 • 7 28 = 7 • 2 • 2 The prime factorization of 28 is 2 • 2 • 7, or 22 • 7 .

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**Factors and Prime Factorization**

Course 1 4-2 Factors and Prime Factorization Check It Out: Example 2B Write the prime factorization of 36. Method 2: Use a ladder diagram. Choose a prime factor of 36 to begin. Keep dividing by prime factors until the quotient is 1. 3 36 3 36 2 12 3 12 2 6 2 4 3 3 2 2 1 1 36 = 3 • 2 • 2 • 3 36 = 3 • 3 • 2 • 2 The prime factorization of 36 is 3 • 2 • 2 • 3, or 32 • 23.

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**Factors and Prime Factorization Insert Lesson Title Here**

Course 1 4-2 Factors and Prime Factorization Insert Lesson Title Here Lesson Quiz List all the factors of each number. 1. 22 2. 40 3. 51 1, 2, 11, 22 1, 2, 4, 5, 8, 10, 20, 40 1, 3, 17, 51 Write the prime factorization of each number. 4. 32 5. 120 25 23 3 5

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