**Greatest Common Factor**

Welcome! September 23, 2013

Objective: I will be able to find the greatest common factor of two whole numbers.

Standard: 6.NS.4 - Finding the greatest common factor.

Factoring Review

Complete the sentence...

Factor Trees Review

Factor trees are used to find the

Prime Factorization

of one number.

Create factor trees for the following numbers in your spiral...

**Greatest Common Factor**

Factors are numbers you multiply to get other numbers.

Finding the Greatest Common Factor (GCF)

Should we find all of the factors in a factor list or create factor trees?

Based on the definitions we have, write down a prediction in your spiral.

You will need the following:

-Math Spiral Notebook

-3 Pencils

Pull out Friday's homework, "Factoring Trees and Prime Factorization," and be prepared to grade it.

Factoring Trees Answers

36

/ \

9 4

/ \ / \

3 3 2 2

Answer: 3, 3, 2, 2

25

/ \

5 5

Answer: 5, 5

72

/ \

8 9

/ \ / \

4 2 3 3

/ \ | | |

2 2 2 3 3

Answer: 2, 2, 2, 3, 3

64

/ \

8 8

/ \ / \

4 2 4 2

/ \ | / \ |

2 2 2 2 2 2

Answer: 2, 2, 2, 2, 2, 2

100

/ \

20 5

/ \ |

4 5 5

/ \ | |

2 2 5 5

Answer: 2, 2, 5, 5

27

/ \

9 3

/ \ |

3 3 3

Answer: 3, 3, 3

Prime Factorization Answers

1. 24 = 2 x 2 x 2 x 3

2. Prime

3. 51 = 3 x 17

4. 66 = 2 x 3 x 11

5. 80 = 2 x 2 x 2 x 2 x 5

6. 45 = 3 x 3 x 5

7. D - Infinite

8. C - Neither prime nor composite.

Factoring is finding the combinations of numbers that _______ together to create a __________ number.

What are the factors of the following numbers?

4? 20? 25?

32 65

/ \ / \

Common Factors are factors you find for two numbers that are the same.

So simply put...

The Greatest Common Factors are the largest Common Factors of two numbers.

In your spiral, let's do both methods together to see which would give us the best results. Create a factor list and a factor tree for...

**24 and 36**

Using the GCF

Finding the Greatest Common Factor of two numbers is important because we do that already in our heads to simplify fractions.

Homework

Complete the worksheet titled, "Finding the Greatest Common Factor."

It is scored out of a possible 13 points.

Have a great day!

KWL

KWL stands for what you

K

now, what you

W

ant to know, and what you have

L

earned.

In your math spiral, write a list of what you

K

now about the Greatest Common Factor.

Then underneath your list, write 1 questions about what you

W

ant to know.

KWL

In your spiral, write a complete sentence describing what you have

L

earned about the Greatest Common Factor.

*Remember to include words such as, "And," "But," "Because," and "Or."

You Do

Find the GCF for...

36 and 78

45 and 63

28 and 84

* You can use either method*

Closure

I can find the greatest common factor of two or more numbers by using...

Finding the greatest common factor is important because it...