Cambridge Primary Checkpoint 0845 · Topic 7 of 10

2D and 3D shapes and angles

Properties of triangles, quadrilaterals, polygons and circles, 3D shapes and nets, and calculating angles.

📌 Key points

Angles are measured in degrees (°). Acute: less than 90°. Right angle: exactly 90°. Obtuse: between 90° and 180°. Reflex: more than 180°.
Angles on a straight line add up to 180°. Angles around a point add up to 360°.
The three angles inside any triangle add up to 180°.
Equilateral triangle: 3 equal sides and 3 angles of 60°. Isosceles: 2 equal sides and 2 equal angles. Scalene: no equal sides.
Quadrilaterals have 4 sides and their angles add up to 360°, e.g. square, rectangle, rhombus, parallelogram, trapezium and kite.
A regular polygon has all sides and all angles equal. Pentagon: 5 sides, hexagon: 6, heptagon: 7, octagon: 8.
The radius goes from the centre of a circle to its edge. The diameter goes across through the centre and is twice the radius.
3D shapes have faces, edges and vertices. A cube has 6 faces, 12 edges and 8 vertices.
A net is a flat shape that folds up to make a 3D shape, e.g. 6 squares can fold into a cube.

Vertex: A corner where sides or edges meet (plural: vertices).
Parallel: Lines that are always the same distance apart and never meet.
Perpendicular: Lines that meet at a right angle (90°).
Polygon: A flat, closed shape with straight sides.
Regular: With all sides equal and all angles equal.
Net: A flat pattern that can be folded to make a 3D shape.
Prism: A 3D shape with the same cross-section all the way through, e.g. a triangular prism.
Diameter: A straight line across a circle through its centre. It is twice the radius.

Two angles of a triangle are 48° and 75°. Find the third angle and say what type of angle it is.

💡 Test tip

Before measuring or calculating an angle, decide if it looks acute or obtuse. This stops you reading the wrong scale on a protractor.

Test yourself8 questions from a bank of 23. A new mix every time.