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NumberFix: Persuasive mathematical writing based on Harry Potter

A Writing Across the Curriculum Lesson from NumberFix
Math Topic: measurement & proportional reasoning Students Write: a persuasive justification

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Just How Big
is Hagrid?

using persuasive writing in math

This writing across the curriculum lesson was written by NumberFix Coordinator, Holly Young, who believes it would work well with students in grades 5-12. Check out Holly's Making Mathematicians website.

This lesson was proposed to NumberFix using this template. If you have a math/mentor text lesson you'd like to have published, fill out the template and send it to Holly Young, our NumberFix Coordinator: We'll send you an NNWP Print Publication if we post your lesson here!

Lesson Overview & Objective:

Students explore the ideas and development rubric with persuasion included, assessing a previously written problem. With their knowledge of good persuasive writing, students will critically read a section of Harry Potter and use mathematics and the evidence from the reading to decide on the size of the character Hagrid. Students create a life size cut-out of Hagrid, writing their explanation of work according to the state ideas and development portion of the writing rubric.


Essential Questions for this Lesson:

What qualities do you see in good persuasive writing? Can you use persuasive writing to validate a solution to a problem (using measurement and proportional reasoning)? How can learning about persuasive writing help you in math?


Writing skills to stress while teaching this lesson:

  • Idea Development (writing with a central idea or theme in mind; putting learned information and research into one's own words)
  • Organization (beginning the writing with a strong introduction; ending the writing with a satisfying conclusion by linking the conclusion back to the introduction)

Materials List:

Setting the Stage:

Any introduction to persuasive writing or persuasive speaking is a benefit to start this lesson. Visit WritingFix's Persuasive Writing Homepage for ideas on persuasive writing.

Teacher Instructions:

  • Have the class brainstorm on the following question: what qualities do you see in good persuasive writing? Really point students to the idea of evidence or supported proof.
  • Put two problems on the board and ask the students to work with a partner to solve:
    • A 2-inch by 3-inch picture needs to be enlarged so that the length of one side is 4 inches, what does the other side have to be in order to keep the picture from looking distorted?
  • As a class, discuss possible answers to each problem, highlighting equivalent fractions and the idea of proportional when items enlarge or reduce.
  • Pass out the Idea and Content Development/Persuasion Rubric. Ask students to highlight or circle key words in the ‘5’ category. Discuss the underlined and bolded summary sentences. Repeat this reading and highlighting process for a ‘3’ and a ‘1’ paper.
  • Pass out the three student exemplars about proportions and have the students read over each response and score it a 1,3, or 5. Let the class discuss and share why they scored each answer as they did. The first problem should receive a 3 because it isn’t giving proof; it is rambling and it doesn’t explain how it got the numbers that it did. The second problem should receive a 1 – it has some explanation, but the problem is done incorrectly and the explanation isn’t addressing how the problem was solved. The last answer should receive a 5. Make sure the class is clear on what constitutes evidence.
  • Pass out the Read,Write, Reflect graphic organizer. Read the problem that the students are going to solve outloud (How big is Hagrid?). Have them look over the “Read” header before they hear the text to start making some decisions about how to solve the problem.
  • Pass out copies of the text, Harry Potter and the Sorcerer’s Stone, pages 82 – 85. Instruct students to highlight what they think is important information as the teacher reads the passage aloud.
  • Read the passage aloud to the students. After reading, have students work in partners and share what they highlighted and why. Have the students read the problem again and re-read the passage together, looking for additional pieces to highlight.
  • Students need to talk about and jot down ideas in the “write” column about what information they need to solve and how they are going to solve the problem.
  • Hand out the solving graphic organizer. Also, students will need measuring tapes, rulers, calculators, and meter/yard sticks. Make sure that you model writing evidence from text or self in the graphic organizer.
  • Once students have their measurements for Hagrid, they are to write an explanation paragraph(s) for their measurements INDIVIDUALLY. I focus them on the idea/development rubric as they write.
  • Once each partner set is finished writing, they exchange their papers and score each other using the idea development Post-it® Note-sized templates.
  • As a partner set, they analyze what each person did well, and use highlighters to choose parts of each person’s writing in order to create one explanation that would score a 5. They may need to work together to add any additional writing.

  • Students now will create a full-size tracing of Hagrid, using their measurements. (I use large pieces of butcher paper for this portion. Some students need to tape two sheets side by side)

  • When the outline is drawn, students write their final explanation paragraph inside it, combining the best of both of their papers.

  • The outlines are hung up on the wall. Students use their ideas/persuasion rubric to grade two other Hagrids (not their own). I had the students write their scores on Post-it® Note-sized templates and put them directly on the cut-outs.
  • As a class, analyze some explanations and see why they may be scored 3’s and what can be done to improve upon them so that they would definitely score a 5.
  • Exit ticket (I have students fill out in the “Reflect” section of the Read, Write, Reflect Graphic Organizer): Have students answer: How can learning about persuasive writing help you in math?

Student Samples:

Below, find a close-up photo of one student sample written by 5th and 6th graders. Below that, find three pairs of 5th and 6th graders posing in front of their Hagrid-sized work.

If you have an excellent sample that you can photograph and send to us after teaching this lesson, we'll say "Thanks!" by sending you a copy of one of the NNWP's Print Resources for your classroom. Contact Holly ( if you're interested.

(written by a Erin and Austin, a 5th and 6th grader)

(Erin and Austin pose in front of their work)


(Conner and Zack pose in front of their work)


(Kimberly and Brady pose in front of their work)



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