1. Warm Up 1. 50, 6 2. 105, 7 3. List the factors of 28. no yes
1. 50, , 7
3. List the factors of 28.
Tell whether each number is prime or composite. If the number is composite, write it as the product of two numbers.
Tell whether the second number is a factor of the first number no
yes
±1, ±2, ±4, ±7,
±14, ±28
4. 11
prime
5. 98
composite; 49  2

2. Simplify.
A. 4–3
B. 70
C. (–5)–4
D. –5–4

3. Learning Target
Students will be able to:Write the prime factorization of numbers and find the GCF of monomials.

4. The whole numbers that are multiplied to find a product are called factors of that product. A number is divisible by its factors.
You can use the factors of a number to write the number as a product. The number 12 can be factored several ways.
Factorizations of 12
1 12 
2 6
3 4

5. The order of factors does not change the product, but there is only one example below that cannot be factored further. The circled factorization is the prime factorization because all the factors are prime numbers. The prime factors can be written in any order, and except for changes in the order, there is only one way to write the prime factorization of a number.
Factorizations of 12
1 12 
2 6
3 4

6. A prime number has exactly two factors, itself and 1
A prime number has exactly two factors, itself and 1. The number 1 is not prime because it only has one factor.
Remember!

7. Write the prime factorization of 98.
98 = 2  72

8. Write the prime factorization of each number.

9. Write the prime factorization of each number.
d. 19

10. Factors that are shared by two or more whole numbers are called common factors. The greatest of these common factors is called the greatest common factor, or GCF.
Factors of 12: 1, 2, 3, 4, 6, 12
Factors of 32: 1, 2, 4, 8, 16, 32
Common factors: 1, 2, 4
The greatest of the common factors is 4.

11. The GCF of 100 and 60 is 20. Find the GCF of each pair of numbers.

12. The GCF of 26 and 52 is 26. Find the GCF of each pair of numbers.

13. The GCF of 15 and 25 is 5. Find the GCF of each pair of numbers.

14. You can also find the GCF of monomials that include variables
You can also find the GCF of monomials that include variables. To find the GCF of monomials, write the prime factorization of each coefficient and write all powers of variables as products. Then find the product of the common factors.

15. Find the GCF of each pair of monomials.
15x3 and 9x2

16. Find the GCF of each pair of monomials.
8x2 and 7y3

17. If two terms contain the same variable raised to different powers, the GCF will contain that variable raised to the lower power.
Helpful Hint

18. Find the GCF of each pair of monomials.
18g2 and 27g3

19. Find the GCF of each pair of monomials.
16a6 and 9b

20. A cafeteria has 18 chocolate-milk cartons and 24 regular-milk cartons
A cafeteria has 18 chocolate-milk cartons and 24 regular-milk cartons. The cook wants to arrange the cartons with the same number of cartons in each row. Chocolate and regular milk will not be in the same row. How many rows will there be if the cook puts the greatest possible number of cartons in each row?
The 18 chocolate and 24 regular milk cartons must be divided into groups of equal size. The number of cartons in each row must be a common factor of 18 and 24.
The GCF of 18 and 24 is 6.

21. The greatest possible number of milk cartons in each row is 6
The greatest possible number of milk cartons in each row is 6. Find the number of rows of each type of milk when the cook puts the greatest number of cartons in each row.
18 chocolate milk cartons
6 containers per row
= 3 rows
24 regular milk cartons
= 4 rows
When the greatest possible number of types of milk is in each row, there are 7 rows in total.