Beacon Lesson Plan Library

Prime Time

Lisa Richardson
Leon County Schools


This activity is a fun way to practice determining the prime factorization of composite numbers. The students create Christmas factor trees for prime numbers greater than 100.


The student determines the prime factorization of a composite number.


-Pencil, one per student
-One box of crayons, markers, or colored pencils per student
-Several sheets of clean unlined paper
-White poster board, one per student
-Peer Critique Form, one per student (see associated file)
-Copy of checklist, one per student (see associated file)
-Glitter in several colors


1. Gather materials for activity (see materials list).

2. Make copies of the Peer Critique Form, one per student (see associated file).

3. Make copies of the Performance Checklist, one per student (see associated file).

4. Make a copy of the Example for teacher use (see associated file).


Note: You may use other religious graphics on the tree, i.e. Hanukkah Tree.
1. Show students pictures of decorated and undecorated Christmas trees.

2. Ask the students how Christmas trees relate to math.

3. Guide them to see that a factor tree resembles a Christmas tree.

4. Distribute Performance Checklists to students and instruct them to write their names on their papers. Go over criteria ensuring students understand the expectations.

5. Distribute materials (pencil and paper) for factor tree rough draft.

6. Instruct students to form pairs or groups of three.

7. Explain and model prime factorization of composite numbers greater than 100 (see example in associated file).

8. Explain and model how to compare like terms of prime factorizations to create exponents.

9. Explain and model how to write prime factorization in exponential notation.

10. Tell the students that both prime and composite numbers should continue to the next level of the tree until all of the branches yield prime numbers (this factor tree will resemble a Christmas tree).

11. Tell the students to select a composite number greater than 100.

12. Allow the students to write their composite number on their rough draft papers.

13. Allow the students time to create their rough drafts of their Christmas factor trees.

14. Circulate around the room formatively assessing studentsí work by observation and provide guidance to students who need additional help.

15. Distribute Peer Critique Forms (see associated file) to the students. Instruct the students to write their name on their papers.

16. Guide students to have their partners complete the Peer Critique Form once their rough draft is finished.

17. Tell students to read their peer critique forms and discuss the results with their peers.

18. Tell students to bring their peer critique forms to the teacher for approval before beginning their final products. This is another method of formative assessment.

19. Remind students that the final product is designed on poster board.

20. Tell students to begin working on their final product, after the peer critique form has been discussed with their partners and the teacher.

21. Tell students to outline their final products in pencil before decorating.

22. Tell the students to decorate their final products with markers, crayons, colored pencils, and/or glitter, and glue.

23. Formatively assess using Performance Checklists and review Peer Critique Forms.


Use the completed Christmas factor tree and peer critique form to formatively assess the studentís ability to determine the prime factorization of a composite number.

The checklist in the attached file includes the criteria for a successful performance.

Note: Students who are not successful in this activity may need additional practice determining the prime factorization of composite numbers.
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