6th Grade Math Textbook, Progress

Write all the common factors for each set of numbers.

1. 8 and 24 2. 10 and 30 3.15 and 35 4. 12 and 18


2. 16 and 20 6. 12 and 24 7.30 and 18 8. 45 and 20


3. 4, 6, and 8 10. 6, 9, and 12 11.5, 12, and 14 12. 6, 14, and 22

Find the GCF and the GCD of each set of numbers.

13. 6 and 12 14. 12 and 36 15.8 and 10 16. 6 and 14


14. 9 and 30 18. 8 and 36 19.24 and 42 20. 7 and 40


15. 8, 24, and 32 22.5, 30, and 35 23.15, 30, and 45

Update your skills. See page 3.

Greatest Common Factor

6-5

The greatest common factor (GCF) of two or more numbers

is the greatest number that is a factor of all of the numbers.

Find the greatest common factor of 8, 12, and 20.

To find the GCF:

List all the factors 0 8: 1 , 2 , 4 , 8

of each number. 12: 1 , 2 , 3, 4 , 6, 12

20: 1 , 2 , 4 , 5, 10, 20

Find the common Common factors:

factors. 1 , 2 , 4

Choose the greatest The greatest common

common factor. factor is 4.

The GCF of 8, 12, and 20 is 4.

You can also refer to the greatest common factor of two or

more numbers as the greatest common divisor (GCD).

The GCD of 8, 12, and 20 is 4. Think

4 divides evenly into 8, 12, and 20.

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