Every composite number can be written as the product of prime factors. Such a product is the prime factorization of the number. A factor tree can be useful for finding the prime factorization of a number. An example of a factor tree for 45 is given at the right. Step 1-(5) Step 2 Describe what happens in Step 1 of the factor tree for 45. Why is the 5 circled but not the 9? 2.) Describe what happens in Step 2. Why do the branches stop at the circled numbers? 3) What is the prime factorization of 45? 1. Complete the factor tree for 120 at the right. Why are more branches necessary to make this tree than to make the one for 45? What is the prime factorization of 120? Chapter 4 Activity 3 10 120 45 12 (3) Sketch a factor tree of your own for 120 that starts with a different pair of factors. 63 Compare the circled numbers at the ends of the branches in the two factor trees for 120. What do you notice? Copyright 2013 Pearson Education, Inc. All rights reserved.