1. 40 56 18 36 54 10/8/08 GCF, LCM Using Prime Factors #19
Add the above heading to graph paper and your table of contents, then find the prime factorization of each number below.
Today’s Plan:
Warm-up and review
Practice!
Assignment: #1-14 all on graph paper showing all work including factor tree and prime factorization line up.
Reminders:
Use pencil!
Quiz tomorrow

2. Using Prime Factorization to Find the GCF and LCM
Write the prime factorization of
each number and circle the
common factors.
40 = 2 · 2 · 2 · 5
56 = 2 · 2 · 2 · 7
2 · 2 · 2 = 8
Multiply the common prime factors.
The GFC is 8.
2 · 2 · 2 · 5 · 7
8 · 5 · 7
40 · 7
The LCM is 280.

3. Insert Lesson Title Here
Find the GCF and LCM
B. 18, 36, 54
18 = 2 · 3 · 3
36 = 2 · 2 · 3 · 3
54 = 2 · 3 · 3 · 3
2, 3, 3
2 · 3 · 3
6 · 3 18
18 · 2 · 3
36 · 3
The LCM is 108.
The GCF is 18.

4. Using Prime Factorization to Find the GCF
Course 2
2-5
Greatest Common Factor
Using Prime Factorization to Find the GCF
Find the greatest common factor (GCF).
B. 252, 180, 96, 60
Write the prime factorization
of each number and circle
the common prime factors.
252 = 2 · 2 · 3 · 3 · 7
180 = 2 · 2 · 3 · 3 · 5
96 = 2 · 2 · 2 · 2 · 2 · 3
60 = 2 · 2 · 3 · 5
2 · 2 · 3 = 12
Multiply the common prime
factors.
The GCF is 12.

5. Insert Lesson Title Here
Course 2
2-5
Greatest Common Factor
Insert Lesson Title Here
Find the greatest common factor (GCF).
A. 72, 84
72 = 2 · 2 · 2 · 9
Write the prime factorization of each number and circle the common factors.
84 = 2 · 2 · 7 · 3
2 · 2 = 4
Multiply the common prime factors.
The GCF is 4.

6. Insert Lesson Title Here
Course 2
2-5
Greatest Common Factor
Insert Lesson Title Here
Find the greatest common factor (GCF).
B. 360, 250, 170, 40
360 = 2 · 2 · 2 · 9 · 5
Write the prime factorization
of each number and circle
the common prime factors.
250 = 2 · 5 · 5 · 5
170 = 2 · 5 · 17
40 = 2 · 2 · 2 · 5
Multiply the common prime
factors.
2 · 5 = 10
The GCF is 10.

7. Using Prime Factorization to Find the LCM
Course 2
2-6
Least Common Multiple
Using Prime Factorization to Find the LCM
Find the least common multiple (LCM).
B. 14, 35, 49
14 = 2 · 7
Write the prime factorization of
each number.
35 = 5 · 7
Circle the common prime factors.
49 = 7 · 7
List the prime factors, using
the circled factors only once.
2, 5, 7, 7
2 · 5 · 7 · 7
Multiply the factors in the list.
The LCM is 490.

8. Insert Lesson Title Here
Course 2
2-6
Least Common Multiple
Insert Lesson Title Here
Find the least common multiple (LCM).
A. 50, 130
50 = 2 · 5 · 5
Write the prime factorization of
each number.
110 = 2 · 5 · 11
Circle the common prime factors.
List the prime factors, using
the circled factors only once.
2, 5, 5, 11
2 · 5 · 5 · 11
Multiply the factors in the list.
The LCM is 550.

9. Using Prime Factorization to Find the LCM
Course 2
2-6
Least Common Multiple
Using Prime Factorization to Find the LCM
Find the least common multiple (LCM).
A. 60, 130
60 = 2 · 2 · 3 · 5
Write the prime factorization of
each number.
130 = 2 · 5 · 13
Circle the common prime factors.
2, 2, 3, 5, 13
List the prime factors, using
the circled factors only once.
2 · 2 · 3 · 5 · 13
Multiply the factors in the list.
The LCM is 780.