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Understand prime and composite numbers, use models and factor pairs, find prime factorization of numbers. Practice identifying common factors and GCF through examples.
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Five-Minute Check (over Lesson 9–1) Main Idea and Vocabulary Example 1: Use Models Example 2: Use Factor Pairs Example 3: Find the Prime Factorization of a Number Lesson Menu
I will identify prime and composite numbers. • prime factorization Main Idea/Vocabulary
Use Models Tell whether the number 14 represented by the model is prime or composite. The model shows 2 rows of 7 squares. The squares could also be arranged in 7 rows of 2 squares, 14 rows of 1 square, or 1 row of 14 squares, as shown below. Answer: So, the number 14 is a composite number because it has more than 2 factors. Example 1
A B Tell whether the number 8 represented by the model is prime or composite. • prime • composite Example 1
Use Factor Pairs 19 square tables are to be placed together to form a rectangle. Is 19 a prime or composite number? What does it mean in this problem? factors of 19: 1, 19 Answer: Since the number 19 only has two factors, it is a prime number. This means there is only one way to place the tables. Example 2
A B 24 tables are to be placed together to form a rectangle. Is 24 a prime or composite number? • prime • composite Example 2
Find the Prime Factorization of a Number Find the prime factorization of 54. 54 54 2 × 27 3 × 18 2 × 3 × 9 3 × 3 × 6 2 × 3 × 3 × 3 3 × 3 × 3 × 2 Answer: In order, the prime factorization of 54 is 2 × 3 × 3 × 3. Example 3
A B C D Which shows the prime factorization of 81? • 2 × 3 × 3 • 2 × 2 × 3 × 9 • 3 × 3 × 3 × 3 • 9 × 9 Example 3
End of the Lesson End Lesson
Five-Minute Check (over Lesson 9–1) Image Bank Math Tool Chest Compare Fractions Resources
A B C D (over Lesson 9–1) Find the common factors of 12 and 18. • 1, 2, 3, 6, 9 • 1, 2, 3, 4, 6, 9 • 1, 2, 3, 6 • 6, 9 Five Minute Check 1
A B C D (over Lesson 9–1) Find the common factors of 20, 24, and 28. • 1, 2, 4 • 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14 • 1, 2, 3, 4, 6, 12, 14 • 2, 4 Five Minute Check 2
A B C D (over Lesson 9–1) Find the GCF of 15 and 20. • 4 • 5 • 3, 5 • 1, 5 Five Minute Check 3
A B C D (over Lesson 9–1) Find the GCF of 21, 28, and 35. • 1, 3, 4, 6, 7 • 3 • 1, 7 • 7 Five Minute Check 4