Grade 6 Mathematics Geometry – Lines Notes

Mathematics — Geometry

Subtopic: Lines (for learners aged 11)

Objectives:

• Know what a line, line segment and ray are.
• Recognise parallel, perpendicular and intersecting lines.
• Identify collinear points and the midpoint of a segment.

Key words and symbols

• Line: extends forever in both directions. Symbol: AB with a ↔ above it (written as AB ↔).
• Line segment: part of a line with two end points. Symbol: AB with a bar above it (AB).
• Ray: starts at one point and goes on forever in one direction. Symbol: AB with an arrow on the right (AB →).
• Parallel lines: lines that never meet. Symbol: ∥
• Perpendicular lines: lines that meet at a right angle (90°). Symbol: ⟂
• Collinear: points that lie on the same straight line.
• Midpoint: the point exactly in the middle of a segment.

Simple diagrams

Worked examples (easy)

1. Is the figure with arrows on both ends a line, a ray or a segment? Answer: a line.
2. Are these lines parallel? (Two horizontal lines) Answer: Yes — they never meet.
3. Points D, E, F lie on the same straight road. What do we call them? Answer: collinear points.

Practice questions

1. Draw a line and mark two points P and Q on it. Label the line PQ ↔.
2. Draw a segment CD, then mark and name its midpoint M.
3. Give an example (draw) of a ray. Name its starting point and direction.
4. Are the following true or false?
   • a) Two perpendicular lines meet at 90°.
   • b) Parallel lines always meet.
5. State whether the points A(1), B(2), C(3) on the same straight line are collinear. (Explain in words.)
6. Draw two intersecting lines and label the point of intersection X.

Answers (brief)

1. Answer depends on the student's drawing — should show a straight line with arrows both ends, points P and Q on it.
2. Midpoint M is the point exactly between C and D so CM = MD.
3. A ray looks like this: starting point A and an arrow towards B (A→B). Starting point is A.
4. a) True. b) False — parallel lines never meet.
5. Yes — if A, B and C are on one straight line they are collinear (they lie on the same line).
6. Should show two lines crossing with their intersection labelled X.