TOPIC 2 · GRADE 3 FOUNDATION
Parallel, Intersecting, and Perpendicular Lines
Recognize how pairs of lines behave in shapes, maps, buildings, and patterns.
MA.3.GR.1.1BIG IDEA
Parallel lines stay the same distance apart. Intersecting lines cross. Perpendicular lines are a special intersecting pair that makes square corners.
WHAT TO KNOW
- Parallel lines never meet when extended on a flat plane.
- All perpendicular lines intersect, but not all intersecting lines are perpendicular.
- A paper corner or square tile is a useful right-angle checker.
WATCH OUT
Lines that merely cross are not automatically perpendicular; they must form 90° angles.
TRY IT
Change the crossing angle and watch when the relationship becomes perpendicular.
Choose the next topic from the lesson rail when you are ready.