M3.5.2 For the adult
Angles and parallel lines
A road crosses two parallel railway tracks. I know one angle. Can I find the other seven?
What this chapter teaches
When a line crosses two parallel lines, the eight angles have only two sizes. Corresponding angles (an F shape) are equal. Alternate angles (a Z shape) are equal. Angles side by side on a straight line add to 180°.
Three questions to ask
There is no one right wording. Listen for the idea.
- Where have you seen parallel lines, and how would you mark them on a drawing?
- One angle is 70°. How do you find an angle that corresponds to it?
- How can you tell an alternate pair from a corresponding pair?
After the chapter, the learner can
- Find equal angles where a line crosses two parallel lines
- Name alternate and corresponding angles
What they copy into their notebook
A line across parallel lines makes two sizes of angle. Corresponding angles (F) are equal. Alternate angles (Z) are equal. Angles side by side add to 180°.