Cogito
Grade 4 Math · Chapter 7 · Lesson 4
Lines, Rays, and Segments
Three things that all look like a straight line.
10 problems · about 14 minutes · 4.G.A.1
What this lesson teaches
The child identifies points, lines, line segments, and rays, and tells parallel from perpendicular.
- A line goes on forever, a segment stops, a ray does one of each.
- Parallel lines never meet.
- Perpendicular lines cross at a right angle.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Angles Add Together: A right angle split into 25 and one more part. How big is that part?
Answer 65
Why 65 degrees.
Review — Naming and Measuring Angles: Is 75 degrees acute or obtuse?
Answer Acute.
Why 75 degrees is acute.
Warm Up
Straightforward practice. Get the method working first.
4 problemsAt how many degrees do perpendicular lines cross?
Answer 90
Why 90 degrees.
Which goes on forever in both directions?
Answer A line.
Why A line has no end points.
Which has exactly two end points?
Answer A segment.
Why It stops at both ends.
Which has one end point and goes on forever?
Answer A ray.
Why Like a beam of light.
Build It Up
The same ideas with more to keep track of.
2 problemsAt how many degrees do perpendicular lines cross?
Answer 90
Why A right angle.
Do parallel lines ever meet?
Answer No.
Why They stay the same distance apart.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Tracks: Railway tracks never meet. What are they called?
Answer Parallel.
Why Parallel lines never meet.
The Corner: Two lines cross at 90 degrees. What are they called?
Answer Perpendicular.
Why Perpendicular lines cross at a right angle.