Transcript Lesson Title

Greatest Common Factor
LESSON 4-4
Course 1
Additional Examples
List the factors to find the GCF of 48 and 64.
List the factors of 48 and the factors of 64.
Then circle the common factors.
Factors of 48: 1 , 2 , 3, 4 , 6, 8 , 12, 16 , 24, 48
The common factors are
Factors of 64: 1 , 2 , 4 , 8 , 16 , 32, 64
1, 2, 4, 8, and 16.
The greatest common factor (GCF) is 16.
Greatest Common Factor
LESSON 4-4
Course 1
Additional Examples
Use a division ladder to find the GCF of 84 and 90.
2 84
3 42
14
90
45
15
Divide by 2, a common factor of 84 and 90.
Divide by 3, a common factor of 42 and 45.
14 and 15 have no common factors.
Multiply the common factors: 2  3 = 6.
The GCF of 84 and 90 is 6.
Greatest Common Factor
LESSON 4-4
Course 1
Additional Examples
Use factor trees to find the GCF of 28 and 42.
42
28
2
14
14
2
7
28 = 2
42 = 2
7
3
Make a factor tree for each number.
2
 2 7
 3 7
Write the prime factorization for each number.
Identify common factors.
2  7 = 14
Multiply the common factors.
The GCF of 28 and 42 is 14.