The idea, step by step
Look for smaller pieces
A composite shape is made by joining simpler shapes. A house outline can be split into a rectangle and a triangle. The pieces join without a gap. Drawing a helpful dividing line can make a complicated outline easier to describe.
Flat shapes and solid objects
A flat shape has length and width. A solid object also has depth. A toy rocket might combine a cylinder body and a cone nose. Name the actual solid pieces, not only the flat shapes you see in one drawing. Different sensible partitions can describe the same object.
A common trap
A drawing of an object is the object itself.
Instead: A drawing is flat; the object it represents may have depth. Describe solid pieces as solids.
See the thinking
A house shape
Describe the two shapes in the supplied house outline.
- Use the dashed line to split the outline.
- The upper piece has three sides, so it is a triangle.
- The lower piece has four right angles, so it is a rectangle.
A model tower
A model has a cylinder body with a cone placed on top. Which two solids form it?
- Identify the round body as a cylinder.
- Identify the pointed top as a cone.
Check your understanding
A shape is made by placing two squares side by side along a full edge. What overall shape is formed?
Show answer
A rectangle.
The joined outline has four right angles and two longer opposite sides.
Your turn
6 questions · 9 marks · Work at your own pace.
Read the questions online
- Name the two component shapes shown in the house diagram.1 mark
- Two identical squares are joined along one full edge. Name the outside shape.1 mark
- A toy is made from one cube body and one pyramid roof. Name its two solid pieces.1 mark
- Can a rectangle be split into two triangles? Describe a line that does this.2 marks
- A student calls a cylinder-and-cone tower “a circle and a triangle”. Explain what is missing.2 marks
- Draw one composite shape made from two rectangles. Show the join.2 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Name the two component shapes shown in the house diagram.1 mark
The dashed line separates the three-sided roof from the rectangular body.
A triangle and a rectangle. - Two identical squares are joined along one full edge. Name the outside shape.1 mark
The shared edge is inside the combined shape.
A rectangle. - A toy is made from one cube body and one pyramid roof. Name its two solid pieces.1 mark
Both pieces have depth, so use solid names.
A cube and a pyramid. - Can a rectangle be split into two triangles? Describe a line that does this.2 marks
The diagonal divides the rectangle into two three-sided parts.
Yes. Draw a diagonal joining opposite corners. - A student calls a cylinder-and-cone tower “a circle and a triangle”. Explain what is missing.2 marks
The tower has depth.
The names describe flat shapes, not the solid pieces. Use cylinder and cone. - Draw one composite shape made from two rectangles. Show the join.2 marks
The two rectangles touch along an edge without overlapping. Other valid drawings are possible.
One valid answer is an L-shape made from a tall rectangle and a shorter rectangle beside its bottom.
Curriculum reference & lesson scope
Australian Curriculum v9 / SA Curriculum Mathematics 2026
Composite shapes/objects; angle names; reflection/rotational symmetry; creating designs.
Official curriculum source ↗