1. 4.3 Greatest Common Factors (GCF)
I can find the greatest common factor of a set of numbers

2. Review
A factor is number that is multiplied by another number to get a product

3. The greatest common factor is the largest factor that two or more numbers share.
Factors of 24:
Factors of 36:
Common factors: 1, 2, 3, 4, 6, 8,
12, 24 1, 2, 3, 4, 6, 9,
12,
18, 36
1, 2, 3, 4, 6, 12
The greatest common factor (GCF) of 24 and 36 is 12.
Example 1 shows three different methods for finding the GCF.

4. Additional Example 1A: Finding the GCF
Find the GCF of the set of numbers.
28 and 42
Method 1: List the factors.
factors of 28:
factors of 42:
List all the factors. 1, 2, 4, 7,
14, 28 1, 2, 3, 6, 7,
14,
21, 42
Circle the GCF.
The GCF of 28 and 42 is 14.

5. Find the GCF of the set of numbers.
Check It Out: Example 1A
Find the GCF of the set of numbers.
18 and 36
Method 1: List the factors.
factors of 18:
factors of 36:
List all the factors. 1, 2, 3, 6, 9, 18 1, 2, 3, 4, 6, 9,
12,
18, 36
Circle the GCF.
The GCF of 18 and 36 is 18.

9. Try on your Own
16 & 28
24 & 56

10. Guided: using Distributive Property

11. Try on your own = =

12. LCM
LCM: Least Common Multiple: The smallest number, other than zero, that is a multiple of two or more given numbers

13. Guided Practice
5 & 6
9 & 11

14. Try on Your own
3 & 7
4 & 6