1. 7-3 Common Factors
and GCF
Math Notes
Number Sense 2.4

2. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.

3. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
STEP ONE: List the factors of 18.

4. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
STEP ONE: List the factors of 18.
18:

5. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
STEP ONE: List the factors of 18.
18: 1,2,3,6,9,18

6. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
18: 1,2,3,6,9,18

7. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
STEP TWO: List the factors of 27.
18: 1,2,3,6,9,18

8. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
STEP TWO: List the factors of 27.
18: 1,2,3,6,9,18
27:

9. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
STEP TWO: List the factors of 27.
18: 1,2,3,6,9,18
27: 1,3,9,27

10. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
18: 1,2,3,6,9,18
27: 1,3,9,27

11. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
STEP THREE: Find the common factors in both list.
18: 1,2,3,6,9,18
27: 1,3,9,27

12. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
18: 1,2,3,6,9,18
27: 1,3,9,27

13. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
18: 1,2,3,6,9,18 Which is the
greatest
27: 1,3,9,27 between
1,3,9 ?

14. Example
Find the Greatest Common Factor (GCF)
of 18 and 27.
18: 1,2,3,6,9,18 Which is the
greatest
27: 1,3,9,27 between
1,3,9 ?
GCF is 9

15. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.

16. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
STEP ONE: List the factors of 15.

17. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
STEP ONE: List the factors of 15.
15:

18. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
STEP ONE: List the factors of 15.
15: 1,3,5,15

19. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
15: 1,3,5,15

20. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
STEP TWO: List the factors of 20.
15: 1,3,5,15

21. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
STEP TWO: List the factors of 20.
15: 1,3,5,15
20:

22. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
STEP TWO: List the factors of 20.
15: 1,3,5,15
20: 1,2,4,5,10,20

23. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
15: 1,3,5,15
20: 1,2,4,5,10,20

24. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
STEP THREE: Find the common factors in both list.
15: 1,3,5,15
20: 1,2,4,5,10,20

25. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
15: 1,3,5,15
20: 1,2,4,5,10,20

26. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
15: 1,3,5,15 Which is the
greatest
20: 1,2,4,5,10,20 between
1 and 5 ?

27. Example
Find the Greatest Common Factor (GCF)
of 15 and 20.
15: 1,3,5,15 Which is the
greatest
20: 1,2,4,5,10,20 between
1 and 5 ?
GCF is 5

28. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.

29. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
STEP ONE: List the factors of 27.

30. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
STEP ONE: List the factors of 27.
27:

31. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
STEP ONE: List the factors of 27.
27: 1,3,9,27

32. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
27: 1,3,9,27

33. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
STEP TWO: List the factors of 36.
27: 1,3,9,27

34. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
STEP TWO: List the factors of 36.
27: 1,3,9,27
36:

35. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
STEP TWO: List the factors of 36.
27: 1,3,9,27
36: 1,2,3,4,9,12,18,36

36. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
27: 1,3,9,27
36: 1,2,3,4,9,12,18,36

37. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
STEP THREE: List the factors of 45.
27: 1,3,9,27
36: 1,2,3,4,9,12,18,36

38. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
STEP THREE: List the factors of 45.
27: 1,3,9,27
36: 1,2,3,4,9,12,18,36
45:

39. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
STEP THREE: List the factors of 45.
27: 1,3,9,27
36: 1,2,3,4,9,12,18,36
45: 1,3,5,9,15,25

40. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
27: 1,3,9,27
36: 1,2,3,4,9,12,18,36
45: 1,3,5,9,15,25

41. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
STEP FOUR: Find the common factors in all 3 lists.
27: 1,3,9,27
36: 1,2,3,4,9,12,18,36
45: 1,3,5,9,15,25

42. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
27: 1,3,9,27
36: 1,2,3,4,9,12,18,36
45: 1,3,5,9,15,25

43. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
27: 1,3,9,27
36: 1,2,3,4,9,12,18,36
45: 1,3,5,9,15,25 Which is the
greatest
between
1,3,9 ?

44. Example
Find the Greatest Common Factor (GCF)
of 27, 36, and 45.
27: 1,3,9,27
36: 1,2,3,4,9,12,18,36
45: 1,3,5,9,15,25 Which is the
greatest
between
GCF is 9 1,3,9 ?