M3.5.1 For the adult
Angles on a line and round a point
Two sticks cross on the ground. One angle is 40°. Can I find the other three without measuring?
What this chapter teaches
Angles that fill a straight line add to 180°, and angles that fill a full turn add to 360°. Where two straight lines cross, opposite angles are equal.
Three questions to ask
There is no one right wording. Listen for the idea.
- Two angles fill a straight line and one is 75°. What is the other, and how do you know?
- Where two straight lines cross, one angle is 40°. What are the other three?
- Why do angles round a point add to 360° and not 180°?
After the chapter, the learner can
- Find a missing angle on a straight line
- Find a missing angle round a point
- Find the opposite angles where two straight lines cross
What they copy into their notebook
Angles on a straight line add to 180°. Angles round a point add to 360°. Where two straight lines cross, opposite angles are equal.