The note
How schools teach it now
Year 6 facts: angles on a straight line add up to 180°, around a point to 360°, in a triangle to 180° and in a quadrilateral to 360°; vertically opposite angles are equal. 11+ diagrams are often 'not drawn to scale', so calculate rather than measure.
5-minute kitchen-table activity
Tear the three corners off a paper triangle and put the points together: they always make a straight line (180°). Then open a door or a pair of scissors to make acute, right, obtuse and reflex angles.
Worked example
A triangle has angles of 48° and 75°. What is the third angle?
- The angles in a triangle add up to 180°.
- 48 + 75 = 123.
- 180 − 123 = 57.
Answer: 57°
Common mistakes to watch for
- Measuring a diagram marked 'not drawn to scale'.
- Using 360° for a triangle or 180° for a quadrilateral.
- Reading the wrong scale on a protractor.
Encouragement
- Try saying
- “Which angle fact could help us here?”
- Rather than
- “Just measure it.”