3D Shapes β€” Boxes, Nets, and Sketches

Mathematics

Class 5 | CBSE, NCERT & ICSE

Learning Objectives

Introduction β€” 2D vs 3D

In earlier classes, you learned about 2D (flat) shapes like squares, rectangles, triangles, and circles. These have only length and width β€” they lie flat on paper. But the real world is 3D! A box, a ball, a tin can, an ice cream cone β€” these are all 3D shapes (also called solids). They have length, width, AND height (or depth).

A net is what a 3D shape looks like when you "unfold" it flat. Imagine cutting open a cardboard box along its edges and flattening it β€” that flat pattern is the net of the box. Knowing about nets helps in packaging, gift wrapping, building, and even in space engineering (ISRO folds solar panels flat for launch, then unfolds them in space)!

Image needed: Comparison of 2D shapes vs 3D shapes: show a square next to a cube, a circle next to a sphere, a rectangle next to a cuboid, a triangle next to a triangular prism. Clear arrows labelling "2D (flat)" and "3D (solid)".
Style: Clean side-by-side comparison diagram, colourful
Size: 700Γ—350px

Common 3D Shapes

ShapeFacesEdgesVerticesReal-Life Examples (India)
Cube6 (all squares)128Rubik's cube, dice, sugar cube, Maggi bouillon cube
Cuboid6 (rectangles)128Brick, book, tiffin box, shoe box, phone
Cylinder3 (2 circles + 1 curved)20Water bottle, Bournvita tin, pillar, pipe, rolling pin
Cone2 (1 circle + 1 curved)11 (apex)Ice cream cone, party hat, traffic cone, temple gopuram
Sphere1 (all curved)00Cricket ball, globe, ladoo, marble, Earth
Triangular Prism5 (2 triangles + 3 rectangles)96Toblerone box, tent, prism in science lab
Square Pyramid5 (1 square + 4 triangles)85Pyramids of Egypt, roof of a hut
Image needed: All 7 common 3D shapes drawn clearly with labels: cube, cuboid, cylinder, cone, sphere, triangular prism, square pyramid. Each shape shown in 3D perspective with faces slightly shaded, edges visible, vertices marked with dots.
Style: Clean 3D diagrams with labels, multicolour shading
Size: 750Γ—400px

Key Terms

  • Face: A flat surface of a 3D shape (can also be curved)
  • Edge: A line where two faces meet
  • Vertex (plural: vertices): A point where edges meet (a corner)

Euler's Formula

The Swiss mathematician Leonhard Euler discovered a beautiful relationship between faces, vertices, and edges of any polyhedron (a 3D shape with flat faces):

Euler's Formula: F + V βˆ’ E = 2

Faces + Vertices βˆ’ Edges = 2 (always!)

Let's verify for the shapes we know:

ShapeF (Faces)V (Vertices)E (Edges)F + V βˆ’ E
Cube68126 + 8 βˆ’ 12 = 2 βœ“
Cuboid68126 + 8 βˆ’ 12 = 2 βœ“
Triangular Prism5695 + 6 βˆ’ 9 = 2 βœ“
Square Pyramid5585 + 5 βˆ’ 8 = 2 βœ“
Triangular Pyramid (Tetrahedron)4464 + 4 βˆ’ 6 = 2 βœ“

Note: Euler's formula works for all polyhedra (flat-faced 3D shapes). It does NOT work for shapes with curved surfaces (sphere, cylinder, cone) β€” those are not polyhedra.

Nets of 3D Shapes

A net is a flat 2D pattern that can be folded to make a 3D shape. When you cut a 3D shape along some edges and unfold it, you get its net.

Net of a Cube

A cube has 6 square faces. Its net is 6 connected squares arranged so they can fold into a cube. There are exactly 11 different nets of a cube!

The most common net looks like a cross (+) with 4 squares in a row and 1 square on each side of the second square.

Image needed: Show the 11 different nets of a cube, each drawn as connected squares on a grid. Number them 1–11. Also show one net with an arrow indicating how it folds into a cube.
Style: Grid-based diagrams, each net in a different colour, compact arrangement
Size: 700Γ—500px

Net of a Cuboid

A cuboid has 6 rectangular faces: 2 each of 3 different sizes (lengthΓ—width, lengthΓ—height, widthΓ—height). Its net shows all 6 rectangles connected.

Example 1: A cuboid is 5 cm long, 3 cm wide, and 2 cm tall. Describe its net.

Solution: The net will have:

  • 2 rectangles of 5 cm Γ— 3 cm (top and bottom)
  • 2 rectangles of 5 cm Γ— 2 cm (front and back)
  • 2 rectangles of 3 cm Γ— 2 cm (left and right sides)

These 6 rectangles are arranged connected along their edges so they fold into the cuboid.

Net of a Cylinder

A cylinder unfolds into: 2 circles (top and bottom) + 1 rectangle (the curved surface unfurled). The rectangle's width = height of cylinder, and its length = circumference of the circular base (2Ο€r).

Net of a Cone

A cone unfolds into: 1 circle (the base) + 1 sector (fan-shaped piece from the curved surface).

Image needed: Four net diagrams side by side: (1) Cube net (cross shape), (2) Cuboid net, (3) Cylinder net (2 circles + rectangle), (4) Cone net (circle + sector). Each with dotted fold lines and an arrow showing the folded 3D shape.
Style: Clean diagrams with fold lines, each net in a different colour
Size: 750Γ—400px

Views of 3D Shapes

When you look at a 3D object from different directions, you see different 2D shapes. The three standard views are:

ViewDirectionWhat You See
Front viewLooking at the object from the frontHeight Γ— Width (face facing you)
Side viewLooking from the left or right sideHeight Γ— Depth
Top view (Plan)Looking from directly aboveWidth Γ— Depth

Example 2: What are the front, side, and top views of a cylinder standing upright?

Solution:

  • Front view: Rectangle (height Γ— diameter)
  • Side view: Rectangle (same as front)
  • Top view: Circle

Example 3: What are the front, side, and top views of a cone standing on its base?

Solution:

  • Front view: Triangle
  • Side view: Triangle
  • Top view: Circle (with a dot in centre for the apex)
Image needed: A visual showing a cube, cylinder, and cone with arrows pointing to their front, side, and top views. Each 3D shape on the left, with 3 view boxes (Front, Side, Top) on the right showing the 2D shape you'd see.
Style: Three-column diagram for each shape, clear labels, educational
Size: 700Γ—500px

Key Words

WordMeaning
3D Shape / SolidA shape with length, width, and height (takes up space)
FaceA flat (or curved) surface of a 3D shape
EdgeA line segment where two faces meet
VertexA point where three or more edges meet (corner)
NetA 2D pattern that folds into a 3D shape
PolyhedronA 3D shape with all flat faces (no curves)
PrismA 3D shape with two identical parallel ends and rectangular sides
PyramidA 3D shape with a polygon base and triangular sides meeting at a point
Cross-sectionThe shape you get when you slice through a 3D object
Euler's FormulaF + V βˆ’ E = 2 (for any polyhedron)

Key Points to Remember

  • 3D shapes have length, width, AND height. 2D shapes have only length and width
  • A cube has 6 faces (squares), 12 edges, 8 vertices. A cuboid has 6 faces (rectangles)
  • A net is a flat pattern that folds into a 3D shape
  • A cube has 11 different possible nets
  • Euler's formula: F + V βˆ’ E = 2 (works for all polyhedra)
  • Cylinder net = 2 circles + 1 rectangle. Cone net = 1 circle + 1 sector
  • Three standard views: Front, Side, Top (also called Plan)
  • A sphere has only 1 curved surface β€” no edges, no vertices
  • The cylinder's rectangle length = circumference = 2Ο€r
  • Cross-sections help visualize what's inside a 3D shape

Finished learning? Now test what you know!