The idea, step by step
Close the shape
A flat shape has a boundary. Join the ends so the shape is closed.
A triangle has three straight sides and three corners. You can join three dots to make one.
Make shapes in different ways
Draw a square with four equal straight sides and four square corners. A rectangle also has four square corners; its sides do not all have to be equal.
A circle has a curved boundary and no corners. Turning a shape does not change its name.
A common trap
A triangle must point upwards.
Instead: Triangles can point in any direction. Check the three straight sides and three corners.
See the thinking
Make a triangle
What must you check after joining the three dots?
- Count the three sides and three corners.
- Make sure the last side meets the first.
Turn a square
A square is turned so one corner points up. Is it still a square?
- Turning does not change its side lengths or corners.
- It still has four equal sides and four square corners.
Check your understanding
Can a closed shape with four straight sides be a triangle?
Show answer
No.
A triangle has three straight sides.
Your turn
6 questions · Work at your own pace.
Read the questions online
- In the picture, which letter marks the triangle?
- Draw a triangle pointing down.
- How many straight sides do you need to make a square?
- Draw a circle. How many corners does it have?
- A child draws three lines but leaves a gap at one corner. What should be fixed?
- Make two different-looking triangles. Explain why both are triangles.
Read the worked solutions
- In the picture, which letter marks the triangle?
A has three straight sides and three corners.
A. - Draw a triangle pointing down.
Check three straight sides meet at three corners.
Answers vary: a closed triangle with one vertex pointing down. - How many straight sides do you need to make a square?
A square has four equal straight sides.
4. - Draw a circle. How many corners does it have?
Its boundary curves all the way around.
0 corners. - A child draws three lines but leaves a gap at one corner. What should be fixed?
The sides must meet to make a closed triangle.
Join the lines to close the gap. - Make two different-looking triangles. Explain why both are triangles.
Size and direction can change while the shape stays a triangle.
Answers vary: each has three straight sides and three corners.
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 ↗