Triangles and Their Properties
Year 5 students classify triangles by their side lengths and angles, exploring properties of equilateral, isosceles, scalene, right-angled, and obtuse triangles.
What You Need to Know
Key Concept Diagram
An equilateral triangle has three equal sides and three equal angles of 60°
An isosceles triangle has exactly two equal sides and two equal base angles
A scalene triangle has no equal sides and no equal angles
The angles inside any triangle always add up to 180°
Key Vocabulary
Equilateral
A triangle with three sides and three angles all equal
Isosceles
A triangle with exactly two equal sides and two equal angles
Scalene
A triangle with no equal sides and no equal angles
Vertex
A corner point where two sides of a shape meet
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
A triangle has angles of 60°, 60°, and 60°. What type is it?
Question 2
A triangle has sides 5 cm, 5 cm, and 8 cm. What type is it?
Question 3
A triangle has angles 90°, 45°, and 45°. What is TRUE about this triangle?
Key Concepts Summary
- ●An equilateral triangle has three equal sides and three equal angles of 60°
- ●An isosceles triangle has exactly two equal sides and two equal base angles
- ●A scalene triangle has no equal sides and no equal angles
- ●The angles inside any triangle always add up to 180°