Cross-sections of prisms
Compare the parallel cross-sections of objects and recognise that slices of a right prism taken parallel to its end (base) faces are all congruent to those faces, while parallel slices of pyramids and cones change in size
Lesson
Set out your lesson
“Cross-sections of prisms means practising the idea at the table with counters or paper models and one clear check. We will demo once, then your child tries.”
Bring to the table
- Unit cubes or squared paper nets
- Pencil for recording
Extra for the adult
Worked example. A 2 by 3 by 4 cuboid has volume 24 unit cubes.
Optional challenge. For Cross-sections of prisms, add one harder example after success.
What to notice. Keep one parent note: examples tried; results; support used. This session samples Cross-sections of prisms, not mastery.
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1 approach
Cross-sections of prisms means practising the idea at the table with counters or paper models and one clear check. We will demo once, then your child tries.
Materials: Unit cubes or squared paper nets; Pencil for recording. 1. Say the goal of Cross-sections of prisms in plain words once. 2. Adult builds a 2×3×4 cuboid and counts 24 unit cubes. 3. Child builds or sketches three cuboids/nets and records length×width×height. 4. Fresh check: one fresh L×W×H volume. Record and stop. Done: three correct volume or net records. Proof: parent note of examples and results. Stop: End after the fresh check; keep optional challenge for another day.
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Start practiceCross-sections of prisms practice
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Learning resources
Extra practice links — they do not replace Gakuva’s teaching approach.
BBC Bitesize · Practice link — not the full lesson
KS3 Maths
Before you open · source notes
KS3 Maths supports Cross-sections of prisms. An adult previews and guides; this is a learning page, not a scored quiz.
Free educational page, no sign-in required for the tested path.
Before you openAsk the learner one fact they learned and one question they still have.
Opening this link does not save learning or assess mastery.
Source, access and review notes
Public BBC Bitesize page. An anonymous GET on 2026-11-12 returned HTTP 200 with no login or payment prompt for this URL. Opening the link does not save practice or assess mastery. An adult should preview and guide the learner.
BBC Bitesize. “KS3 Maths.” External page; Gakuva does not copy, host, embed, or redistribute materials.
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Check understanding
- Slice a play-dough triangular prism parallel to its triangular end faces and show every slice is congruent to the end face
- Explain why slices of a square pyramid taken parallel to its base get smaller towards the apex
- Identify which of an unsharpened hexagonal pencil, a cone and a cereal box give congruent slices when cut parallel to their end faces
“If your child cuts slices off a rectangular block of cheese, parallel to its end, can they explain why every slice is the same rectangle as the end — but slices of an ice-cream cone would keep getting smaller?”
Curriculum record
- Type
- Conceptual
- Subject
- Mathematics
- Domain
- Geometry
- Age range
- Ages 11–12
Standards