2. Finding the Greatest Common Factor
Grade 5

3. Lesson Objectives The student will be able to:
Find the Greatest Common Factor (GCF) for The given Numbers

4. Think Backwards… Find Factors Circle Common Factors
Group Greatest Factor

5. Step 1: Find the Factors For 24 & 36 24 ( 1,2,3,4,6,8,12,24)
36 ( 1,2,3,4,6,9,12,18,36)

6. Step 2: Circle Common Factors
24 ( 1,2,3,4,6,8,12,24)
36 ( 1, 2,3,4,6,9,12,18,36)

7. 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

8. The Greatest Common Factor of 24 and 36 is…12

9. Now let’s try finding the GCF

10. 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

11. 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

12. 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

13. The Greatest Common Factor of 12 and 24 is …

14. Your turn! Find the Greatest Common Factor of 16 and 20.
Remember…Find Factors, Circle Common, Group Greatest!

15. The Greatest Common Factor of 16 and 20 is…4

16. Are you ready?
Let's try some more!

17. Greatest Common Factor
Two Numbers
Factors
Common Factors
Greatest Common Factor
9 and 12
9 : 1,3,9 12: 1,2,3,4,6,12
1,3 3

18. Greatest Common Factor
Two Numbers
Factors
Common Factors
Greatest Common Factor
6 and 18
6: 1,2,3,6 18: 1,2,3,6,9,18
1,2,3,6 6

19. What is the greatest common factor of 45 and 105?

20. What is the greatest common factor of 6 and 15?
Question 1
Numbers (Year 5, Easy)
What is the greatest common factor of 6 and 15?
Use pen and paper to work out the answer

21. What is the greatest common factor of 24 and 40?
Use pen and paper to work out the answer