Start here

Look at a railway track. Do the two rails ever meet?

Part I, Chapter 5 of your book is Parallel and Intersecting Lines.

What you will learn

• Two straight lines meet once, or never meet at all.
• Parallel lines never meet, and keep the same gap.
• A crossing makes four angles. Two pairs face each other and match.
• Angles on a line add to 180°. All round a point, 360°.
• A line across two lines makes eight angles, with three named pairs.
• Those pairs match only when the two lines are parallel.
• You can walk from one known angle to another. Each step uses one named fact.
• Lines at a right angle are perpendicular. A small square marks the corner.
• Two lines perpendicular to a third line are parallel. You can draw them with a set square or by folding paper.
• A bend between two parallels is the sum of two marked angles. Both ends lie on one side.

Quick catch-up

These help.

• What is an angle? (Lines and Angles). The turn between two rays with one shared start.
• Measuring an angle (Lines and Angles). A full turn is 360°. A protractor measures an angle.
• A square corner (Playing with Constructions). Measure a square corner. Do not guess it.