Finding the Greatest Finding the Greatest Common FactorCommon Factor

Finding the Greatest Finding the Greatest Common FactorCommon Factor

Grade 5Grade 5

Lesson Objectives

• The student will be able to:Find the Greatest Common Factor

(GCF) for The given Numbers

Think Backwards…

•Find Factors•Circle Common Factors•Group Greatest Factor

Step 1: Find the FactorsFor 24 & 36

•24 ( 1,2,3,4,6,8,12,24)•36 ( 1,2,3,4,6,9,12,18,36)

Step 2: Circle Common Factors

• 24 ( 1,2,3,4,6,8,12,24)• 36 ( 1, 2,3,4,6,9,12,18,36)

Step 3: Group the Greatest Factor

• 24 – 1,2,3,4,6,8,12,24• 36 – 1,2,3,4,6,9,12,18,36

The Greatest Common The Greatest Common Factor of 24 and 36 is…Factor of 24 and 36 is…The Greatest Common The Greatest Common Factor of 24 and 36 is…Factor of 24 and 36 is…

1212

Now let’s try finding the GCF

Find the GCF of 12 and 24• Step 1: Find the

factors|

• 12 – 1,2,3,4,6,12

• 24 – 1,2,3,4,6,8,12,24

Find the GCF of 12 and 24

• Step 2: Circle the common factors

• 12 – 1,2,3,4,6,12• 24 –

1,2,3,4,6,8,12,24

Find the GCF of 12 and 24

• Step 3: Group the greatest factor

• 12 – 1 ,2, 3, 4, 6, 12• 24 – 1 , 2, 3, 4, 6, 8 ,

12,24

The Greatest The Greatest CommonCommon

Factor of Factor of 1212 and and 2424 is …is …

The Greatest The Greatest CommonCommon

Factor of Factor of 1212 and and 2424 is …is …1212

Your turn!• Find the Greatest Common Factor

of 16 and 20.

• Remember…Find Factors, Circle Common, Group Greatest!

The Greatest The Greatest Common Factor of Common Factor of 1616

and and 2020 is… is…

The Greatest The Greatest Common Factor of Common Factor of 1616

and and 2020 is… is…

44

Are you ready?Are you ready?Are you ready?Are you ready?

Let's try some more!

Two Number

sFactors

Common

Factors

Greates

tCommon Factor

9 and 12

9 : 1,3,912: 1,2,3,4,6,12

1,3 3

Two Number

sFactors

Common

Factors

Greatest

Common Factor

6 and 18 6: 1,2,3,618: 1,2,3,6,9,18

1,2,3,6 6

•What is the greatest common factor of 45 and 105?

•15 25

35 45

What is the greatest common factor of 6 and 15?

2 3

6 15

Question 1Numbers (Year 5, Easy)

•What is the greatest common factor of 24 and 40?

4 6

8 12