--- title: "Comparing 2-D and 3-D shapes" description: "Analyse and compare 2-D and 3-D shapes using informal language to describe sides, vertices, and other attributes" canonical: https://lightmysky.com/learn/mathematics/comparing-2-d-and-3-d-shapes-mt_yGv8doDAmp source: https://lightmysky.com/learn/mathematics/comparing-2-d-and-3-d-shapes-mt_yGv8doDAmp.md retrieved: 2026-11-11 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Comparing 2-D and 3-D shapes Analyse and compare 2-D and 3-D shapes using informal language to describe sides, vertices, and other attributes Subject: Mathematics · Area: Geometry · Ages 5 to 6 Page: https://lightmysky.com/learn/mathematics/comparing-2-d-and-3-d-shapes-mt_yGv8doDAmp ## Ready when they can - Describe and count straight sides and corners of flat shapes, including a circle with none - Compare flat shapes using side and corner counts, including triangles, rectangles and squares - Compare flat shapes with solids using faces, curved parts and corners, including a cube's square faces ## Lesson: Comparing flat and solid shapes On a flat shape, a straight side runs from one corner to the next. A corner is where sides meet. A circle has no straight sides or corners. Choose a starting place when counting. Count each side or corner once. Stop when you get back to the start. *(drawing: Mia checks the playground triangle. It has 3 straight sides and 3 corners.)* **Example.** The playground gate is a rectangle with 4 sides and 4 corners. It has two longer sides and two shorter sides. A square also has 4 sides and 4 corners, but all its sides have the same length. A square is a special rectangle. The gate has one more side than the triangle. Turning a shape does not change its counts. A square is flat. A cube-shaped toy is solid. A face is a flat part of a solid's outside. A cube has six square faces and corners, with no curved parts. Each face has the shape of a flat square. A sphere is solid too, but it curves all the way around and has no corners. **Example.** One square face of a cube has 4 corners. The whole cube has 8: 4 on top and 4 underneath. Count the top corners, then keep counting the bottom corners: 5, 6, 7, 8. Include corners hidden in a picture. For the gate display, Mia compares a flat rectangle drawing with a whole cube-shaped toy. Compare the same kind of part: sides with sides, or corners with corners. A face is not a corner. Matching counts do not always mean matching shapes. A square and a rectangle that is not square both have 4 corners. **Example.** For separate shapes, keep counting as you move to the next shape. Count a triangle's sides: 1, 2, 3. Then count a square's sides: 4, 5, 6, 7. There are 7 sides altogether. Each dot below stands for one counted side. Covering a corner does not remove it. Use the whole shape's count to find hidden corners. If a rectangle has 2 corners showing, count on to its full count of 4. Two more corners are hidden. **Example.** You can compare side and corner counts on one flat shape. Count the sides first. Then start a new count for the corners. A rectangle has 4 sides and 4 corners, so these counts match. Keep the counts separate rather than adding them together. **Recap.** Count each part once. Compare sides with sides and corners with corners. A square is flat; a cube is solid with square faces. *Geometry lesson and questions written for this dataset.* ## Practice 18 questions on this page, each with its working shown. ## Needs first - [2-D shapes](https://lightmysky.com/learn/mathematics/2-d-shapes-mt_KJeEeTutJI) - [3-D shapes](https://lightmysky.com/learn/mathematics/3-d-shapes-mt_Qcp2d_kuta) ## Opens up - [Building & Drawing Shapes](https://lightmysky.com/learn/mathematics/building-and-drawing-shapes-mt_2VR963szuk) - [Defining attributes of shapes](https://lightmysky.com/learn/mathematics/defining-attributes-of-shapes-mt_bfhng6mOuy) - [Edges, vertices, and faces](https://lightmysky.com/learn/mathematics/edges-vertices-and-faces-mt_Mnodea7mG_) - [2-D shapes (age 6+)](https://lightmysky.com/learn/mathematics/2-d-shapes-age-6-mt_sBcRdUfAzV) - [Combining Simple Shapes](https://lightmysky.com/learn/mathematics/combining-simple-shapes-mt_XjwUlmxdCT)