Beacon Lesson Plan Library
Prime Factorization Mobile
Amelia McCurdy Santa Rosa District Schools
Description
During this review lesson, students demonstrate their knowledge of prime numbers, composite numbers, and prime factorization using exponents to create a factor tree mobile.
Objectives
The student knows word names and standard numerals for integers, fractions, decimals, ratios, numbers expressed as percents, numbers with exponents, numbers expressed in scientific notation, and numbers expressed using the square root radical.
The student knows if numbers are prime or composite.
The student determines the prime factorization of a composite number.
Materials
3 x 5 Index cards (unlined)
Yarn (cut into 6 to 8 inch lengths)
Colored Pencils, markers, or crayons
Hole puncher
Ceiling Hooks (large paper clips or commercial)
Preparations
1. Prepare a mobile as an example
2. Create sets of prime and composite numbers to assign to students
Procedures
1. Review prime numbers, composite numbers, and prime factorization. Ask students to give you examples of prime and composite numbers. Review how to find the prime factorization using a factor tree and how to write the prime factorization using exponents. Provide opportunity for practice.
2. Describe the project. Assign two numbers to each student, one prime and one composite. After the students determine which numbers are prime and which are composite, they will plan their mobile by drawing a factor tree for the composite number. Encourage students to find several ways to create a factor tree and select one. Students are required to rewrite their number in prime factorization using exponents. Each number on their factor tree is one index card. On the back of their number card, the students will write the number in exponential form. Each line (tree branch) is a piece of yarn. Students need to determine how many cards and pieces of yarn are needed for their mobiles. See attached file for an example mobile.
3. Students will bring their plans to the teacher for approval and tell the teacher how many cards and pieces of yarn are needed for their project. Encourage students to be creative in their designs. For example, write the numbers in 3D form.
4. After the projects are completed and graded, hang the mobiles for display in class.
Assessments
Scoring Rubric of project:
 Whole number correctly rewritten
3 pointscorrect and using exponents
2 pointscorrect and without exponents
0 pointsincorrect
 Identify prime number
3 pointscorrectly identifies prime number
2 pointscorrectly identifies with help
0 pointsincorrect
 Identify composite number
3 pointscorrectly identifies composite number
2pointscorrectly identifies with help
0 pointsincorrect
 Design mobile
3 pointscorrect
2 pointscorrect with help
0 pointsincorrect
Students who do not score at least 8 points will need additional instruction and practice.
Extensions
For lower level students, have students work in cooperative groups. For advanced students, students could create a mobile for numbers greater than 100. For PreAlgebra students, use positive and negative integers. For Algebra students, create a mobile for monomials.
