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LESSON Factors and Prime Factorization 4-2 Lesson Objectives Write prime factorizations of composite numbers Vocabulary factor (p. 169) prime factorization (p. 169) Additional Examples Example 1 List all of the factors of the number. A. 16 Begin listing factors in pairs. 16 16 2 8 16 1 1 is a factor. 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. The factors of 16 are . B. 19 19 The factors of 19 are Copyright © by Holt, Rinehart and Winston. All rights reserved. Begin listing factors in pairs. 19 is not divisible by any other whole numbers. . 72 Holt Mathematics LESSON 4-2 CONTINUED Example 2 Write the prime factorization of each number. A. 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 2 24 • 12 2 • 6 2 • 24 6 3 • 2 3 4 • 2 • 2 24 The prime factorization of 24 is , or . B. 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 3 45 3 15 3 15 55 55 1 1 45 45 The prime factorization of 45 is or . Try This 1. List all factors of the number. 12 Copyright © by Holt, Rinehart and Winston. All rights reserved. 73 Holt Mathematics