Mathematics
Geometry
Procedural
11–13 yrs
Understanding angles (age 11+)
理解角度（11岁以上）
Description
Apply the properties of angles at a point (360°), on a straight line (180°), and vertically opposite angles to find unknown angles in multi-step problems
Mastery Evidence
- Find a missing angle using the fact that angles on a straight line sum to 180°
- Use vertically opposite angles are equal to set up and solve an equation for an unknown
- Combine multiple angle facts in a single diagram to find several missing angles step by step
Assessment Prompt
If your child is given a diagram with several angles marked at crossing lines and some unknown, can they use the rules about straight lines and crossing lines to find all the missing angles step by step?
