MathematicsGeometryAges 6–7

Defining attributes of shapes

Distinguish defining attributes of shapes (e.g. triangles are closed and three-sided) from non-defining attributes (e.g. colour, orientation, overall size)

Lesson

Set out your lesson

Classify triangles by being closed, straight-sided and three-sided, ignoring orientation, colour and size.

Before teaching

Activity

Follow an outline with a finger and distinguish straight from curved lines.

Policy

Directed source edges are preserved, not assumed completed. If the readiness probe is difficult, model with support and record supported practice instead of independent evidence.

Printer, credit, and teaching notes

Materials

Use the supplied stage-specific structured materials. Plain paper and pencil; screen viewing is optional.

Order

Show, guided, put teaching sheet aside, then task sheets in order; adult keys remain private.

Access

No printing or cutting is required unless explicitly choosing a physical construction. Exact paper alternatives are in each material; adaptations change the evidence mode as stated.

Materials are ready in each step. Use them on screen or print just the current step. Put teaching examples aside before the learner tries.

Next: Show

Adult extras

What this lesson covers and its limits

These are bounded opportunities, not learner attainment. Partial and blocked source requirements remain so.

partial: Distinguish defining attributes of shapes (e.g. triangles are closed and three-sided) from non-defining attributes (e.g. colour, orientation, overall size)
Source title 'Angles in triangles' retained unchanged; actual source contract is defining attributes. No angle-sum or degree-measure claim. This is a bounded task opportunity, not established attainment or automatic use across contexts.
partial: Build and draw shapes that possess defining attributes
Mapped task(s) offer this clause only within the supplied examples. Source title 'Angles in triangles' retained unchanged; actual source contract is defining attributes. No angle-sum or degree-measure claim. No attainment or automatic/general performance is claimed.
partial: Identify that a shape remains a triangle regardless of its size, colour, or orientation
Mapped task(s) offer this clause only within the supplied examples. Source title 'Angles in triangles' retained unchanged; actual source contract is defining attributes. No angle-sum or degree-measure claim. No attainment or automatic/general performance is claimed.
partial: Explain why a given shape is or is not a particular type based on its defining properties
Mapped task(s) offer this clause only within the supplied examples. Source title 'Angles in triangles' retained unchanged; actual source contract is defining attributes. No angle-sum or degree-measure claim. No attainment or automatic/general performance is claimed.
partial: Does {{name}} understand that what makes a shape a triangle is having 3 sides and 3 corners — not its colour or which way it's pointing?
Source title 'Angles in triangles' retained unchanged; actual source contract is defining attributes. No angle-sum or degree-measure claim. This is a bounded task opportunity, not established attainment or automatic use across contexts.

Source title 'Angles in triangles' retained unchanged; actual source contract is defining attributes. No angle-sum or degree-measure claim.

Share teaching feedback

Entire curriculum

1858 concepts · 9 subjects

Continue learning

Share and support

Compare teaching approaches

Teaching approaches

Gakuva’s recommended starting approach is selected. You can still compare every option.

1 approach

Selected Default Gakuva

Classify triangles by being closed, straight-sided and three-sided, ignoring orientation, colour and size.

Family records and proof options

Keep a record of your learning

Save photos, notes, and attendance. Export a proof packet for compliance or portfolio reviews.

View learner plans ($12/mo per learner) See sample family archive

Learning resources

Extra practice links — they do not replace Gakuva’s teaching approach.

Illustrative Mathematics · Practice link — not the full lesson

3-D Shape Sort

Open practice(new tab)

Before you open · source notes

Solid shapes are sorted by defining attributes such as faces and edges. Emphasise defining traits, not colour or size.

Free, no sign-in. A teacher solution is on the same page, so use the student view with your child.

Before you open

Ask which attributes define a shape in the sort, and name one non-defining trait to ignore.

Opening this link does not save learning or assess mastery.

Source, access and review notes

Public Illustrative Mathematics task page. The .html address responds HTTP 308 to this URL. An anonymous GET of this URL on 2026-11-12 returned HTTP 200 with no login or payment prompt. Where a teacher solution is present, it is on the same page as the student task; this check did not find a separate locked student view. An adult can use the student view section and should not read a solution aloud. Advertising was not observed in the fetched HTML text; that is not a browser, device, or ad-free guarantee. This is a paper or discussion task, not an automatically marked interactive game. Opening the link does not save practice or assess mastery. Diagrams on the page use missing or filename-only alt text, so they are not an accessible image equivalent. Accessibility still depends on an adult describing the picture.

Illustrative Mathematics. “3-D Shape Sort.” Licensed CC BY-NC-SA 4.0. External task; Gakuva does not copy, host, embed, or redistribute it.

CC BY-NC-SA 4.0 — link only

Check understanding

Build and draw shapes that possess defining attributes
Identify that a shape remains a triangle regardless of its size, colour, or orientation
Explain why a given shape is or is not a particular type based on its defining properties

“Does your child understand that what makes a shape a triangle is having 3 sides and 3 corners — not its colour or which way it's pointing?”

Curriculum record

Type: Conceptual
Subject: Mathematics
Domain: Geometry
Age range: Ages 6–7

Standards

acara-v9:AC9M1SP01ccss-math:1.G.1the-ontario-curriculum-mathematics-2020:ON-MATH-2020-G1-E1.1