How it works
A triangle has three straight sides and is closed all round.
Colour, size and tilt don't matter.
If it has a gap or a curve, it is not a triangle.
Worked examples
Check the sides
- Count the sides: 3 straight sides.
- Check it is closed with no gaps.
- It is a triangle.
A gap
- A shape has 3 sides but one side has a gap.
- It is not closed all round.
- It is not a triangle.
Bigger or turned
- Make a triangle bigger, or turn it on its side.
- It still has 3 straight sides.
- It is still a triangle.
A taste of the worksheet
These are the first problems of set A. The printable sheet has many more, with an answer key.
- Which shape is a triangle?
- Which shape is NOT a triangle?
- How many straight sides does a triangle have? ___
- How many sides does this shape have? ___
- This shape is a triangle.
Words to know
- triangle
- A shape with 3 straight sides.
- side
- A straight edge of a shape.