The idea, step by step
Flat shapes and solid objects
A circle is a flat shape. A ball is a solid object that takes up space.
A picture can show a solid object on a flat page. When we sort, think about the object the picture represents.
Choose a rule
A sorting rule tells us what belongs in each group. You could sort flat shapes into curved boundaries and only straight boundaries.
You can sort solid objects by features too. For example, some have flat surfaces and some are curved all around.
A common trap
A picture of a ball means the ball itself is flat.
Instead: The picture is flat, but it represents a solid ball.
See the thinking
Sort a ball and a circle
Which is a solid object: a drawn circle or a real ball?
- A ball takes up space and can be held.
- The circle is a flat shape.
Sort straight boundaries
Which pictured flat shapes have only straight sides?
- A is a triangle and B and C have four straight sides.
- D is a circle with a curved boundary.
Check your understanding
A cube-shaped block and a drawn square look related. Are both solid objects?
Show answer
No. The block is solid; the square is a flat shape.
The block has depth and takes up space.
Your turn
6 questions · Work at your own pace.
Read the questions online
- Sort these words into flat shapes and solid objects: triangle, ball, square, cube.
- Which pictured object is a cube-shaped block?
- Which pictured flat shape has a curved boundary?
- A child sorts a circle with triangles using the rule only straight sides. Does it belong?
- A can has flat round ends and a curved side. Must it be a ball?
- Choose a fair sorting rule for a square, triangle and circle. Show your groups.
Read the worked solutions
- Sort these words into flat shapes and solid objects: triangle, ball, square, cube.
Think about the named shape or object, not the printed words.
Flat: triangle, square. Solid: ball, cube. - Which pictured object is a cube-shaped block?
A shows flat square faces.
A. - Which pictured flat shape has a curved boundary?
It is a circle.
D. - A child sorts a circle with triangles using the rule only straight sides. Does it belong?
The circle's boundary is curved.
No. - A can has flat round ends and a curved side. Must it be a ball?
A ball is curved all around; a can also has flat ends.
No. - Choose a fair sorting rule for a square, triangle and circle. Show your groups.
State one rule and apply it consistently.
Answers vary: for example, straight boundaries: square and triangle; curved boundary: circle.
Curriculum reference & lesson scope
Australian Curriculum v9 / SA Curriculum 2026
Year 1 making, sorting and describing familiar shapes and objects using spatial features.
Official curriculum source ↗