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Maths for SG Primary Schools

Primary 2 maths · Geometry · About 8 minutes

Recognise cubes, cuboids, cones, cylinders and spheres

Count hidden as well as visible faces and follow their shared edges.

Start the interactive lesson →Open practice activity

What you will learn

Models used: number sentences, stories, diagrams.

Before you start

From flat faces to a solid

A cube has six square faces. Some are hidden when we look from here.

  1. A cube has six square faces. Some are hidden when we look from here.

    A new view can hide or reveal faces without changing the solid. A net must reconnect all faces without gaps or overlaps.

    A cube with three visible and three hidden faces

  2. The flat shapes are the faces of a cube. The joined edges are the folds.

    Imagine opening the edges and laying every face flat. This is a net.

    Fold along shared edges. Faces close the solid without overlaps or gaps.

  3. Fold the squares along their joins. Each face meets its neighbours to close the cube.

    All six faces close without gaps
What did the picture help us see?

Fold the squares along their joins. Each face meets its neighbours to close the cube.

Worked example: A new example, together

Name the solid represented by this drawing.

Use faces and curved surfaces; the drawing shows a three-dimensional object.

  1. Count hidden as well as visible faces and follow their shared edges.

    Six equal square faces, twelve edges and eight vertices.

    Use faces and curved surfaces; the drawing shows a three-dimensional object.

  2. Look at the flat faces and curved surfaces.

    Use faces and curved surfaces; the drawing shows a three-dimensional object.
    Name the solid represented by this drawing.

    cube

  3. Look at the flat faces and curved surfaces.

    Use faces and curved surfaces; the drawing shows a three-dimensional object.

  4. Six equal square faces, twelve edges and eight vertices.

    Use faces and curved surfaces; the drawing shows a three-dimensional object.

  5. These features describe a cube.

    Use faces and curved surfaces; the drawing shows a three-dimensional object.

  6. Check the result against the question we started with.

    Turn the model mentally and check the faces that are hidden.

    We found cube. Six equal square faces, twelve edges and eight vertices.

    Use faces and curved surfaces; the drawing shows a three-dimensional object.

Common mistakes to discuss

Check your understanding

Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.

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