Download Skills Practice 4-2 File - District 196 e

NAME ________________________________________ DATE ______________ PERIOD _____
4-2
Study Guide and Intervention
Greatest Common Factor
The greatest common factor (GCF) of two or more numbers is the largest number that is a factor of
each number. The GCF of prime numbers is 1.
Example 1
Find the GCF of 72 and 108 by listing factors.
factors of 72: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72
factors of 108: 1, 2, 3, 4, 6, 9, 12, 18, 27, 36, 54, 108
common factors: 1, 2, 3, 4, 6, 9, 12, 18, 36
The GCF of 72 and 108 is 36.
Find the GCF of 42 and 60 using prime factors.
Method 1 Write the prime factorization.
Method 2 Divide by prime numbers.
Divide both 42 and 60 by 2.
Then divide the quotients by 3.
60 2 2 3 5
42 2 3 7
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Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
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The common prime factors are 2 and 3. The GCF of 42 and 60 is 2 3, or 6.
Exercises
Find the GCF of each set of numbers.
1. 18, 30
2. 60, 45
3. 24, 72
4. 32, 48
5. 100, 30
6. 54, 36
7. 3, 97, 5
8. 4, 20, 24
9. 36, 9, 45
Chapter 4
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Course 2
Lesson 4–2
Example 2
NAME ________________________________________ DATE ______________ PERIOD _____
4-2
Skills Practice
Greatest Common Factor
1. 14, 20
2. 16, 42
3. 8, 18
4. 24, 36
5. 72, 22
6. 77, 15
7. 32, 80
8. 90, 120
9. 45, 30
10. 12, 62
11. 15, 27
12. 21, 28
13. 12, 20, 26
14. 15, 20, 25
15. 60, 72, 36
16. 32, 48, 64
17. 36, 48, 30
18. 28, 56, 42
19. 80, 110, 90
20. 9, 25, 49
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Find the GCF of each set of numbers.
Find the GCF of each set of algebraic expressions.
21. 21ab, 14b
22. 20a2, 36a
23. 15ab, 5b2
24. 35a2, 85ab
25. Find the GCF of 23 32 5 and 22 3 52.
Chapter 4
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Course 2