Moira’s Birthday - Primary

Primary (Age 6 – 9)

Curriculum Goal

Primary: Number Sense

  • Estimate the number of objects in collections of up to 200 and verify their estimates by counting.
  • Round whole numbers to the nearest ten or hundred, in various contexts.


  • Students practice estimation skills in the context of various birthday party scenarios.
  • Students should be comfortable with rounding whole numbers based on context.


  • Book: Moira’s Birthday by Robert Munsch
    • Jar of small items (e.g. pencils, erasers, beans)
  • Appendix A (Slideshow)



  • Prepare a jar of small items before starting the lesson (see materials).
  • Show students the jar of items lesson and ask them to estimate the number of items in it. Ask what strategies they use for estimating quantities.
  • Invite students to share their understanding of the word “estimation”.
    • An estimate is a number that is reasonably close to the right answer. Estimation is a powerful tool for planning because it can help you quickly determine a numerical quantity that is close to the answer.
  • Ask students the following questions to support their understanding of estimation.
    • Have you ever estimated anything? What do we estimate? (e.g. costs, temperature, distances, amounts)
    • Can you estimate the number of students in our class without counting?
  • Ask students whether they have helped plan a party before. Potential discussion questions include:
    • How many people were invited to the party?
    • What type of food was served at the party?
    • How much food do you estimate was needed for the party? (e.g., Can you estimate how many slices of pizza were needed for all the party guests?)
  • Read Moira’s Birthday to the class.


  • After reading the story, inform students that they will be helping Moira plan a new birthday party.
  • Students will work through different scenarios to help Moira plan her party. Present the slideshow (Appendix A) and read the scenario on the first slide.
  • Suggest to students that they think about their answers before sharing, but should take too much time because the objective is to quickly estimate quantities.
    • Read the “speaker notes” underneath the slides for potential responses.
  • Work through the scenarios on each of the slides using the same procedure.


  • Discuss the various strategies that students used to estimate quantities. Ask students to share their new understandings of estimation as a tool for planning.

Look Fors

  • Are students able to quickly estimate quantities in real-life scenarios?
  • Are students able to round whole numbers to the nearest ten or hundred?
  • Do students justify their estimations using the real-life context of scenarios?


  • Ask students to create their own party scenarios and estimate the number of items required for each scenario.
  • Challenge students to estimate the number of pizzas required for a class party.

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