Kablow!

Geometric language, 2D and 3D shapes

Apprends en jouant

Réponds à ces questions pour gagner de l'énergie, puis pêche et explore. Sans compte.

Pour les enseignants : diapos de leçon, notes de révision prêts à l'emploi pour Geometric language, 2D and 3D shapes (Mathematics, Geometry and measures) — utilise-les en cours, ou lance le thème en activité de classe interactive que tes apprenants jouent en direct.

Notes de leçon

Key Geometric Terms and Notation

  • Point: an exact location, named with a capital letter (e.g., A).
  • Line: a straight path extending infinitely both ways; line segment has two endpoints; ray has one endpoint.
  • Vertex (plural vertices): a corner where two or more edges meet; edge: a line segment where two faces meet.
  • Plane: a flat surface that extends infinitely; a face of a 3D shape lies in a plane.
  • Parallel lines are distinct coplanar lines that never meet. Perpendicular lines meet at 90°, marked with a small square.
  • Congruent shapes have identical size and shape. Similar shapes have corresponding lengths in a constant ratio; scale factor 1 is allowed.
  • Regular polygon: all sides equal and all interior angles equal.

Similar triangles

Similar triangles4 cm3 cm5 cm8 cm6 cm10 cmCorresponding lengths are multiplied by 2.

Properties of 2D Shapes

  • Triangle types: equilateral (3 equal sides, 3 equal angles), isosceles (2 equal sides, 2 equal angles), scalene (no equal sides), right-angled (one 90° angle).
  • Quadrilateral types: square (4 equal sides, 4 right angles), rectangle (opposite sides equal, 4 right angles), parallelogram (opposite sides parallel and equal), rhombus (4 equal sides, opposite angles equal), trapezium (one pair of parallel sides), kite (two pairs of adjacent equal sides).
  • Polygon naming: 3 sides = triangle, 4 = quadrilateral, 5 = pentagon, 6 = hexagon, 8 = octagon.
  • A regular polygon has all sides and angles equal; e.g., regular hexagon has 6 equal sides and 6 equal angles.
  • Interior angle sum of an n-sided polygon = (n − 2) × 180°.
  • Diagonals: lines connecting non-adjacent vertices; a square has 2 diagonals, a pentagon has 5.

Regular hexagon

Regular hexagon4 cm120°

Faces, Edges, and Vertices of 3D Shapes

  • Cube: 6 square faces, 12 edges, 8 vertices.
  • Cuboid: 6 rectangular faces (opposite faces equal), 12 edges, 8 vertices.
  • Triangular prism: 5 faces (2 triangles, 3 rectangles), 9 edges, 6 vertices.
  • Cylinder: 2 circular faces and 1 curved surface; 2 edges (circles), 0 vertices.
  • Cone: 1 circular face, 1 curved surface, 1 vertex (apex), 1 curved edge.
  • Sphere: 1 curved surface, 0 edges, 0 vertices.
  • Square-based pyramid: 5 faces (1 square, 4 triangles), 8 edges, 5 vertices.

Square-based pyramid

Square-based pyramid5 cm4 cmslant height = √(5² + 2²) = 5.39 cm

Prisms and Pyramids

  • A right prism has a constant polygonal cross-section and rectangular lateral faces. The face, edge and vertex formulas below apply to polygonal prisms.
  • Cuboid and cube are special prisms with rectangular cross-sections.
  • A cylinder has a constant circular cross-section, but it is not a polygonal prism.
  • Pyramid: a solid with a polygon base and triangular faces meeting at a common apex; named by its base (e.g., square-based pyramid).
  • A cone has a circular base and curved surface meeting at an apex; it is not a polygon-based pyramid.
  • For a prism, number of faces = (number of sides of cross-section) + 2; edges = 3 × (number of sides); vertices = 2 × (number of sides).
  • For a pyramid with an n-sided base: faces = n + 1, edges = 2n, vertices = n + 1.

Cylinder: flat and curved surfaces

Cylinder: flat and curved surfaces3 cm5 cm

Nets of 3D Shapes

  • A net is a 2D pattern that folds to form a 3D shape.
  • A cube has 11 different nets; each net has 6 squares arranged so they fold without overlap.
  • To check a net: ensure all faces are present and connected, and that folding along edges produces the correct solid.
  • Common nets: cuboid (6 rectangles), triangular prism (2 triangles + 3 rectangles), square-based pyramid (1 square + 4 triangles).
  • Cylinder net: two circles and a rectangle (curved surface unrolled).
  • Cone net: one circle and a sector of a circle.
  • A net must not have flaps that overlap when folded.

A valid cube net

A valid cube netsurface area = 2(9 + 9 + 9) = 54 cm²

Plans and Elevations

  • Plan: the view from directly above (top view).
  • Front elevation: the view from the front.
  • Side elevation: the view from the side (often right side).
  • For a 3D shape made of cubes, draw the outline of each view, showing visible squares.
  • Plan and elevations are 2D drawings that show the shape's dimensions from different directions.
  • Example: a cuboid of length 3, width 2, height 1 has plan 3×2, front elevation 3×1, side elevation 2×1.

Views of a cuboid

Views of a cuboidViewDirectionRectangle / cmPlanFrom above3 × 2Front elevationFrom front3 × 1Side elevationFrom side2 × 1

Common Misconceptions to Avoid

  • A square is a rectangle (it has 4 right angles and opposite sides equal) – don't think they are unrelated.
  • A rhombus with equal sides is not necessarily a square unless all angles are 90°.
  • Here, count flat faces separately from curved surfaces. The circular rims of cylinders and cones are curved edges.
  • When counting edges of a pyramid, remember the base edges plus the slant edges.
  • A net must fold without gaps or overlaps; a misplaced flap makes it invalid.
  • Don't confuse plan (top view) with front elevation (front view).

Typical Exam Questions

  • Name a shape from its properties (e.g., 'I have 4 equal sides and 4 right angles' → square).
  • State the number of faces, edges, and vertices of a given solid (e.g., a triangular prism).
  • Draw the net of a given solid (e.g., a cuboid).
  • Draw the plan and elevations of a 3D shape built from cubes.
  • Identify which of several nets forms a cube (only 11 of many arrangements work).
  • Use correct notation: mark parallel sides with arrows, equal sides with dashes, and right angles with squares.

Diapos

Sign up free to view the lesson slides

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

Questions d'entraînement

Aperçu gratuit — 8 sur 62 questions. Inscris-toi pour toutes les voir.
  1. 1.Which of the following is the correct notation for a point?

    Easy
    • AA
    • BAB
    • C∠ABC
    • Dline l
  2. 2.How many edges does a triangular prism have?

    Easy
    • A6
    • B9
    • C12
    • D5
  3. 3.A square is a type of rectangle.

    Easy

    True or false?

  4. 4.Which of the following is a regular polygon?

    Medium
    • AEquilateral triangle
    • BNon-square rectangle
    • CNon-equilateral isosceles triangle
    • DNon-rectangular parallelogram
  5. 5.Which of the following are properties of a cube? (select all that apply)

    Medium
    • A6 faces
    • B8 vertices
    • C12 edges
    • DAll faces are rectangles
    • EAll faces are squares
  6. 6.Match each solid to its number of flat faces. Count curved surfaces separately.

    Medium
    • Cube
    • Triangular prism
    • Cylinder
    • 6
    • 5
    • 2
  7. 7.Arrange the following shapes in order of increasing number of sides: pentagon, triangle, hexagon, quadrilateral.

    Medium
    • Triangle
    • Quadrilateral
    • Pentagon
    • Hexagon
  8. 8.Match each solid to the correct number of edges.

    Easy
    • Cube
    • Triangular prism
    • Square-based pyramid
    • Cylinder
    • 12
    • 9
    • 8
    • 2

Unlock all 62 questions & more

Crée un compte gratuit pour voir toutes les questions, les diapos, les cartes mémo et les notes de révision de ce thème.

Annales

Les annales d'entraînement pour ce thème arrivent bientôt.
Bientôt disponible