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NumberFix: Math/Writing Lesson based on The Greedy Triangle

A Writing Across the Curriculum Lesson from NumberFix
Math Topic: shapes Students Write: a book about shapes and their uses

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This writing across the curriculum lesson was written by NumberFix Coordinator, Holly Young, who designed it for first grade learners. 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:

After guiding students through an exercise on giving reasons for something being useful, students listen to The Greedy Triangle by Marilyn Burns and determine how triangles and quadrilaterals are useful. Students make books that show where the shapes occur in the world.

Essential Understandings for this Lesson:

  • I can name and sort triangles and quadrilaterals.
  • I can give reasons why each shape is useful.

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)
  • Word Choice (using precise nouns to assist the reader’s understanding; incorporating interesting adjectives into the writing; using strong verbs to keep the sentences interesting)

Materials List:

Setting the Stage:

Students should talk about how people in the community use tools. For example, a carpenter uses a hammer and nails, or a doctor uses a stethoscope.

Teacher Instructions:

  • In a class discussion, have the students talk with a partner about what is a useful tool. From Holly: "I modeled this with another teacher coming up with an unusual tool such as a pencil."
  • Continuing to work with a partner, students will pick one tool and come up with two reasons why the tool is useful. Model the difference between a reason and an opinion. Do some class sharing on a useful tool and the reasons.
  • Fill out the Greedy Triangle Useful Poster Guide on a large poster for the students, using a tool that a partner set had chosen. Decide on two reasons, and write them down on the poster.
  • Read the Greedy Triangle I can Poster together. Discuss which words we know and which words we didn’t know.
  • Read The Greedy Triangle by Marilyn Burns aloud. Before reading, ask the students to listen for the new words from the poster, which were shapes, and see if they could hear how each shape was useful. While reading, stop after a couple of pages and see if the students can point out how each shape is useful, using the illustration to help.
  • After reading, introduce the vocabulary words of triangle and quadrilateral [on page 2 of the Greedy Triangle Useful Poster Guide]. Ask the students to think to themselves about which one is more useful and then share with a partner why either shape is useful.
  • From Holly: "At this point, I asked students to write their own reasons for why a shape was useful. I handed out the Greedy Triangle Notemaker. Students were allowed to pick either the triangle or quadrilateral and fill that word in on the top line, then they had to write reasons why the shape was useful."

  • When students finish writing at least one reason, have them get up and share their writing with a new partner. As a class, share some of the students’ reasons.

  • Give each student a small “book” with the title, My _________ Book. Each page inside should be blank. Ask the students to choose either triangle or quadrilateral and put that on the front cover of their book. For the inside, ask students to look around the classroom and find their chosen shape, draw it in their book, then write where they found it. Some students might stay with one shape throughout the book, others might switch when they felt they had found all the shapes that they were looking for; some students might re-title the book, My Shape Book, and looked for both shapes.


  • After they finish their books, find some physical objects around the room and asked students to show with fingers what shape they saw in the shape that I displayed. (3 fingers for triangles, 4 fingers for quadrilaterals)

Student Samples:

Bella, a first grader

Bella's completed notemaker

From Bella's Book


Carson, a first grader

Carson's completed notemaker

From Carson's book



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