Angle Sum Rules
Know that angles at a point sum to 360° (one whole turn), angles on a straight line sum to 180°, and vertically opposite angles are equal; use these facts to find missing angles
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“If three angles meet at a point and two of them are 120° and 95°, can your child work out the third angle — knowing all the angles at a point add up to 360°?”
Full guide and materials
- Activity. Know that angles at a point sum to 360° (one whole turn), angles on a straight line sum to 180°, and vertically opposite angles are equal; use these facts to find missing angles
What to notice. State that two angles on a straight line add to 180° • Explain that four right angles at a point make 360° • Identify 270° as three right angles
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If three angles meet at a point and two of them are 120° and 95°, can your child work out the third angle — knowing all the angles at a point add up to 360°?
Know that angles at a point sum to 360° (one whole turn), angles on a straight line sum to 180°, and vertically opposite angles are equal; use these facts to find missing angles
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Check understanding
- State that two angles on a straight line add to 180°
- Explain that four right angles at a point make 360°
- Identify 270° as three right angles
“If three angles meet at a point and two of them are 120° and 95°, can your child work out the third angle — knowing all the angles at a point add up to 360°?”
Curriculum record
- Type
- Conceptual
- Subject
- Mathematics
- Domain
- Geometry
- Age range
- Ages 9–10