Understand the idea.
Close the shape
A flat shape has a boundary around it. To make a closed shape, join the ends so there is no gap. Trace all the way round and check you return to your starting point.
A triangle has three straight sides and three corners. Join the three pictured dots with straight lines, including the line back to the first dot. Leaving out that last line would leave the shape open.
Make shapes in different ways
A square has four equal straight sides and four square corners. A rectangle also has four square corners; its sides do not all need to be equal. Look at these features to decide the shape's name.
A circle has a curved boundary with no corners. Turning a shape does not change its sides, corners or curves. A square with one corner pointing upwards is still a square.
See the method in action.
Make a triangle
What must you check after joining the three dots?
Worked solution
- 1
Trace and count the sides.
A triangle needs three straight sides, not curved ones.
- 2
Count the corners.
Each joining point is a corner of the triangle.
- 3
Check that the boundary closes.
The last side must meet the first, leaving no gap around the three dots.
Check that three straight sides join to make a closed shape.
Turn a square
A square is turned so one corner points up. Is it still a square?
Worked solution
- 1
Check what the turn changes.
Turning changes the direction it points, but does not stretch or cut the shape.
- 2
Check the square features.
The side lengths and corners are unchanged by turning.
- 3
Keep the shape name.
Yes, it is still a square because it still has all the square features.
Yes.
Try it yourself.
Check your understanding
Can a closed shape with four straight sides be a triangle?
Show answer & reasoning
No.
No. A triangle has three straight sides. A closed shape with four straight sides has one side too many to be a triangle.
Keep practising
6 worksheet questions
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 ↗