11+ Angles
A small set of angle facts unlocks most 11+ geometry questions. Knowing them instantly is the goal.
The key facts: angles on a straight line add to 180°, angles around a point add to 360°, and the angles in a triangle add to 180°. A right angle is 90°.
Most questions give you all but one angle and ask for the missing one. Identify which rule applies, add the known angles, and subtract from 180° or 360°.
For isosceles triangles, remember the two base angles are equal — this often provides the extra information needed.
Worked examples
Q. Two angles on a straight line are 110° and x. Find x.
Angles on a straight line add to 180°, so x = 180 − 110 = 70°.
Q. A triangle has angles of 40° and 75°. Find the third angle.
Angles in a triangle add to 180°, so third angle = 180 − 40 − 75 = 65°.
Common mistakes
- Using 360° for a straight line (it should be 180°).
- Forgetting that triangle angles total 180°, not 90°.
- Missing the equal base angles in isosceles triangles.
FAQs
Do children need a protractor in the 11+?+
Most 11+ angle questions are solved by reasoning with angle rules rather than measuring, so the facts matter more than the protractor.
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