# Greatest Common Factors

This lesson is about greatest common factors.

First, you will copy the worksheet I have included in this lesson. Then, you will explain the definition of greatest common factor.

Greatest common factor (GCF) is the largest factor of two numbers.

Example:

Factors of 24: 2, 3, 4, 6, 8, 12, 24

Factors of 36: 2, 3, 4, 6, 9, 12, 13, 36

The common factors are 2, 3, 4, 6, and 12.

The greatest common factor is 12.

After you have gone over the examples of greatest common factors, then you can pass out the worksheet.
Worksheet: Greatest Common Factors.

Directions: Write the factors of each number. Then, circle the greatest common factors.

1. Factors of 8:

Factors of 12:

2. Factors of 20:

Factors of 40:

3. Factors of 35:

Factors of 50:

4. Factors of 27:

Factors of 42:

5. Factors of 6:

Factors of 24:

6. Factors of 16:

Factors of 32:

7. Factors of 30:

Factors of 25:

8. Factors of 49:

Factors of 7:

9. Factors of 9:

Factors of 12:

10. Factors of 5:

Factors of 45: Answer Sheet

1. Factors of 8: 1, 2, 4, 8

Factors of 12: 1, 2, 3, 4, 6, 12

The GCF: 4

2. Factors of 20: 1, 2, 4, 5, 10, 20

Factors of 40: 1, 2, 4, 5, 8, 10, 20, 40

The GCF: 20

3. Factors of 35: 1, 5, 7, 35

Factors of 50: 1, 2, 5, 10, 25, 50

The GCF: 5

4. Factors of 27: 1, 3, 9, 27

Factors of 42: 1, 2, 3, 6, 7, 14, 21, 42

The GCF: 3

5. Factors of 6: 1, 2, 3, 6

Factors of 24: 1, 2, 3, 4, 6, 8, 12, 24

The GCF: 6

6. Factors of 16: 1, 2, 4, 8, 16

Factors of 32: 1, 2, 4, 8, 16, 32

The GCF: 16

7. Factors of 30: 1, 2, 3, 5, 6, 10, 15, 30

Factors of 25: 1, 5, 25

The GCF: 5

8. Factors of 49: 1, 7, 49

Factors of 7: 1, 7

The GCF: 7

9. Factors of 9: 1, 3, 9

Factors of 12: 1, 2, 3, 4, 6, 12

The GCF: 3

10. Factors of 5: 1, 5

Factors of 45: 1, 3, 5, 9, 15, 45

The GCF: 5

Each question is worth ten points.

100 to 90 = A

89 to 80 = B

79 to 70 = C

69 to 60 = D

Below 60 = F

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