Classifying shapes by line properties

MathematicsGeometryAges 9–10

Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines, or angles of a specified size; recognise right triangles as a category

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Teaching Table

Set out your lesson

Classify by side relationships and right-angle properties, allowing overlapping categories and rotated figures.

Activity

Ask the learner to draw a pair of parallel lines and a pair of perpendicular lines. Have them indicate a right angle. If they use “looks straight” instead of side relationships, rehearse those ideas before sorting.

If Not Ready

Pause the fresh check. Revisit the named prerequisite or repeat the Show with smaller steps; record supported practice rather than an independent result. Authored predecessor existence never proves this learner is ready.

Allow 25 minutes. Cards are supplied as diagrams and coordinate descriptions; no scissors or printer are needed. Say labels aloud or write groups on spare paper. Grids are exact geometric givens, not a request for ruler measurement.

Use paper or the supplied screen materials in a comfortable place. No special equipment or purchase is needed. Stop or take a break when wanted.

Record the learner’s actual words or work, task ID and any help. Do not prefill success. Allow oral, pointing or written responses as appropriate; oral independent reasoning is not automatically supported. Copied/scribed text is not independent composition or handwriting. No name, account, upload or real family record is required.

Use the complete materials on screen or print only the current sheet. Keep adult guidance out of learner view. Retain an earlier model only when the current step supplies it as context.

Teaching limits and safe use

These are finite task opportunities, not proof of mastery. Record what was attempted and what support was used.

Coordinate-text access changes the task from purely visual recognition to grid/coordinate reasoning; record the mode used.
Finite task opportunities, not learner mastery or universal canonical coverage.
Use the supplied materials on screen or print one current sheet; physical printing can vary.
Record the actual response and assistance; completing a task does not establish mastery.

Use paper or the supplied screen materials in a comfortable place. No special equipment or purchase is needed. Stop or take a break when wanted.

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Classify by side relationships and right-angle properties, allowing overlapping categories and rotated figures.

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Check understanding

Sort a set of quadrilaterals into those with parallel sides and those without
Identify which triangles in a set are right triangles
Classify shapes that have both perpendicular and parallel sides

“If you show your child a mixed set of triangles and quadrilaterals, can they sort them into groups — like "shapes with at least one right angle" or "shapes with parallel sides" — and explain their reasoning?”

Curriculum record

Type: Procedural
Subject: Mathematics
Domain: Geometry
Age range: Ages 9–10