Understand the idea.
Look beyond the outline
A solid takes up space. A flat face is a surface that could lie flat against paper. On solids made of flat faces, an edge is where two faces meet and a vertex is a corner.
A picture may hide some faces behind the solid. Imagine picking it up and turning it over. Count the top and bottom, front and back, and both sides instead of counting only the parts visible in the drawing.
Some surfaces are curved
Some solids have curved surfaces. A cylinder has a flat circular face at each end and a curved surface joining them. A sphere curves all the way around and has no flat face.
Use several features to identify a solid. A cube has six equal square faces. A rectangular box also has flat faces, but its faces need not all be equal squares. Turning the solid does not change its features.
See the method in action.
Cube faces
How many flat faces does a cube have?
Worked solution
- 1
Find the top and bottom.
These are opposite faces, even when the bottom is hidden.
- 2
Count the four faces around the sides.
Front, back, left and right are four more distinct flat faces.
- 3
Add the visible and hidden faces.
All six faces belong to the cube, regardless of which ones the drawing shows.
6 flat faces.
A ball
A ball is shaped like a sphere. Does it have a flat face?
Worked solution
- 1
Consider the sphere from every side.
A ball-shaped sphere keeps a curved surface as you turn it.
- 2
Look for a flat region.
There is no flat surface that matches a sheet of paper.
- 3
State the number of flat faces.
A sphere has a curved surface only, so the answer to the question is no.
No flat faces.
Try it yourself.
Check your understanding
Which solid has two circular flat faces and a curved surface?
Show answer & reasoning
A cylinder
It is a cylinder. Its two ends are flat circles and the surface joining them is curved; both clues must match.
Keep practising
6 worksheet questions
Read the questions online
- Name a solid with six equal square faces.
- How many flat faces does a sphere have?
- How many flat circular faces does a cylinder have?
- Name a real object shaped approximately like a cylinder.
- A drawing shows three cube faces. Does the cube have only three faces? Explain.
- Give one shape difference between a cube and a sphere.
Read the worked solutions
- Name a solid with six equal square faces.
All six faces of a cube are equal squares.
Cube - How many flat faces does a sphere have?
Its surface is curved everywhere.
0 - How many flat circular faces does a cylinder have?
One is at each end.
2 - Name a real object shaped approximately like a cylinder.
A tin has circular ends and a curved side.
Example: a food tin. - A drawing shows three cube faces. Does the cube have only three faces? Explain.
Count the top, bottom and four side faces.
No. It has six faces; three are hidden from this view. - Give one shape difference between a cube and a sphere.
Describe a shape feature rather than a colour or size.
A cube has flat square faces and corners; a sphere has a curved surface and no corners.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum
Solid-object features; comparing/classifying objects; turns; smaller/larger than a right angle.
Official curriculum source ↗