The idea, step by step
Plan the pieces before cutting
List all the faces of the object. Check which faces match and how the edges will join. For a cube, every face is the same square, so every joined edge has the same length.
Draw lightly with a ruler. Fold lines join neighbouring faces; outside lines are cut lines. Add small tabs outside the faces if you want to glue the model. Tabs are not extra faces.
Use dimensions consistently
For a 4 cm by 3 cm by 2 cm box, the faces come in pairs: 4 by 3, 4 by 2, and 3 by 2 cm. A 4 cm edge must join another 4 cm edge.
Test a paper model before decorating it. A drawing that nearly fits can still leave a gap if an edge is measured incorrectly. Allow space for safe cutting and ask an adult if help is needed.
A common trap
A joining tab adds another face to the solid.
Instead: A tab folds inside and holds faces together. It does not cover another outside face.
See the thinking
Make a 2 cm cube
Describe the faces and face area needed for a cube of edge 2 cm.
- A cube has six equal square faces.
- Each square is 2 cm by 2 cm, so its area is 4 square centimetres.
- Six faces use 6 × 4 = 24 square centimetres, excluding joining tabs.
Plan a rectangular box
List the faces of a box 4 cm long, 3 cm wide and 2 cm high.
- Top/bottom: two 4 by 3 cm rectangles.
- Front/back: two 4 by 2 cm rectangles.
- Left/right: two 3 by 2 cm rectangles. Match shared edge lengths when drawing the net.
Check your understanding
How many equal squares must you draw for a cube net?
Show answer
Six.
A cube has six square faces, regardless of tab size.
Your turn
6 questions · 14 marks · Work at your own pace.
Read the questions online
- Draw a valid cube net with square edges 2 cm long. Label each face.3 marks
- Find the total face area of a cube whose edges are 3 cm.2 marks
- A box measures 5 cm by 3 cm by 2 cm. List all six face sizes.3 marks
- A triangular prism has equilateral triangular ends of side 3 cm and length 5 cm. What rectangular side panels are needed?2 marks
- Explain why a 4 cm edge should not be joined to a 3 cm edge without cutting or changing the model.2 marks
- Draw one joining tab on a cube-net sketch and explain whether it counts as a seventh face.2 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Draw a valid cube net with square edges 2 cm long. Label each face.3 marks
Use six equal squares; a row of four with one above and one below the second square is valid.
Check equal shared edges.
Any valid six-square cube net with 2 cm edges. - Find the total face area of a cube whose edges are 3 cm.2 marks
Each face has area 3 × 3 = 9.
Six faces have area 6 × 9 = 54.
54 square centimetres. - A box measures 5 cm by 3 cm by 2 cm. List all six face sizes.3 marks
Use one pair for each pair of dimensions.
Two 5×3 cm; two 5×2 cm; two 3×2 cm. - A triangular prism has equilateral triangular ends of side 3 cm and length 5 cm. What rectangular side panels are needed?2 marks
Each of the triangle's three 3 cm sides extends along the prism's 5 cm length.
Three rectangles, each 3 cm by 5 cm. - Explain why a 4 cm edge should not be joined to a 3 cm edge without cutting or changing the model.2 marks
The 1 cm difference leaves an overhang or a gap.
Their endpoints will not match. - Draw one joining tab on a cube-net sketch and explain whether it counts as a seventh face.2 marks
The cube still has six outside square faces.
The tab is outside an edge and folds inside; it is not another face.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics
Connect objects and two-dimensional nets; construct and explain spatial relationships.
Official curriculum source ↗