Download Factors and Prime Factorization 4-2

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
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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