2D Shape Lesson: The Greedy Triangle


In this lesson, students review geometric terms by making predictions about what the Greedy Triangle will become as the teacher reads the book, The Greedy Triangle. Students will then create geometric creatures after reading the book and discussing the outcome. Another great lesson that links literacy to numeracy.

Australian Curriculum Links:

  • Year 1 – Recognise and classify familiar two-dimensional shapes and three-dimensional objects using obvious features (ACMMG022)
  • Year 2-  Describe and draw two-dimensional shapes, with and without digital technologies (ACMMG042)

Learning outcomes

Students will:

  • review geometric terms by making predictions about how the triangle changes in the book.
  • create an animal using the concepts of the geometric terms that were previously reviewed.
  • analyse the theme of the book.

Teacher planning


45 minutes



  1. Ask the riddle: What did the acorn say when he was all grown up? Answer: Geometry / “Gee, I’m a tree.”
  2. State the objective of the lesson.
  3. Teacher should tell the students that they are to make predictions about what the triangle becomes as the teacher reads the book. Also, tell the students to think about the theme of the book and be able to explain it.
  4. Read the book. Discuss the book’s plot and theme.
  5. Review the words on the vocabulary list.
  6. Teacher Discussion: Back in the days before cameras were invented, the only way you could show someone how something looked was to draw a picture of it. Today, we are going to pretend we are living in those times. Imagine you have just received a letter from an explorer who has discovered a strange animal. The explorer has not sent a drawing just a letter. It is going to be your job to draw a picture of the animal described in the letter. Remember, we are just pretending, so the animal can be really fantastic. Students can name their animals after they create them.
  7. The teacher reads the following sentences one at a time. The students will draw what the teacher describes.
    • The animal has a body shaped like an equilateral triangle.
    • The head is shaped like a bumpy circle.
    • This creature has legs that are approximately one and one-half inches in length.
    • On each leg is a foot with three toes, and on each toe is a claw that is about 1/4 of an inch in length.
    • In the center of its body, it has a large spot shaped like a hexagon.
    • The facial features include a pair of pentagon shaped eyes, an octagon shaped nose and a mouth that is best described as a semicircle.
    • Upon its head are two parallel horns that appear to be sharp.
    • Its tail is furry and one meter in length.


Check the accuracy of the shapes (i.e. pentagon-5 sides, octagon-8 sides,etc.). Have the students write a paragraph supporting the book’s theme with examples from the text.

Supplemental information


This geometric review integrates language arts and math. Most students are better at retaining information when it is attached to something known or relevant. M. Burns presents the shapes in her book using ordinary and familiar things. Also, the shapes are reinforced as the students create their own geometric creatures.

This lesson can become the source for many fourth grade writing objectives, too. The creature could be described in a character analysis, become the main character in an imaginary narrative, be a first person narrator describing a day in his / her life, etc.


Courtesy of http://www.learnnc.org/lp/pages/3385?ref=search and shared under Creative Commons

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