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Mathematics · Grade 3

Shape Categories and Mathematical Explanations

Learners sort quadrilaterals into categories by their attributes (rhombuses, rectangles, squares and others), discover that one shape can belong to several categories (every square is a rectangle and a rhombus), split shapes into parts of equal area named by unit fractions, and practise writing mathematical explanations with a claim, a reason and an example or counterexample.

  • 4 lessons
  • About 85 minutes
  • Shapes and reasoning check: 8 questions
  • Ways to answer: fill in the blanks, choose an answer, match pairs, put in order, shade a shape and sort into groups
See plans Included with Family, Teacher and School plans. Open in PlayOwl

What learners will discover

  • Recognise rhombuses, rectangles and squares as quadrilaterals, and identify quadrilaterals that belong to none of these categories.
  • Explain how shape categories are related, for example that every square is a rectangle and a rhombus but not every rectangle is a square.
  • Partition a shape into parts with equal area and describe each part as a unit fraction of the whole.
  • Write a mathematical explanation with a claim, a reason and an example or a counterexample.

Lessons

  1. Quadrilateral families 5 steps3 practiceabout 22 min
  2. Shapes in more than one category 5 steps3 practiceabout 20 min
  3. Equal areas as fractions 5 steps3 practiceabout 21 min
  4. Explaining like a mathematician 5 steps2 practiceabout 22 min
  5. Shapes and reasoning check 8 questions at the end

Keep exploring

Games to practice with

  • Number-Line HopHelp the frog hop to the right number — from counting to negative fractions.
  • Paint by AnswersSolve each space, dip your brush and watch a picture come to life.
  • Place-Value WorkshopBuild numbers with rods and cubes — and trade ten ones for a ten.

More 3rd grade math

Guide for grown-ups