The idea in brief. Parallel lines stay equally spaced. Perpendicular lines meet at a right angle. Parallel lines need not be horizontal. Perpendicular lines must make a right angle. In the lesson. In the last lesson, you compared angles with the corner of a square. A set square has a corner that is a right angle too. Today, we will learn to spot perpendicular lines and parallel lines. Perpendicular lines meet at a right angle. Parallel lines stay the same distance apart, so they never meet.
Lesson video, with the working
Line pairs
4 min 39 s
The film teaches 3 questions in turn. Each question shows first; its working is written as the film explains it.
Harpreet draws two train tracks, JK and LM, and a road, PQ, on a square grid. Is PQ parallel or perpendicular to JK? Is LM parallel or perpendicular to JK?
JK and PQ meet at a right angle.
PQ is perpendicular to JK.
The gap between JK and LM stays the same.
LM is parallel to JK.
Ans: PQ is perpendicular to JK. LM is parallel to JK.
Example 1 of 2
On a map, road RS crosses road TU. Are RS and TU perpendicular? Write Yes or No.
RS and TU do not meet at a right angle.
No, RS and TU are not perpendicular.
Ans: No
Example 2 of 2
On a map drawn on a square grid, GH is a train track. CD and EF are roads. Which road is parallel to GH?
The gap between GH and EF changes.
The gap between GH and CD stays the same.
CD is parallel to GH.
Ans: CD
How to solve it
For lines that cross, put the corner of a set square where they meet, with one edge along one line.
If the other line lies exactly along the other edge, they meet at a right angle. They are perpendicular, marked with a small square.
For lines that do not meet, count the squares between them in two places on the grid.
If the gap stays the same, the lines are parallel and never meet. Mark them with matching arrowheads.
If the gap changes, the lines are not parallel.
Perpendicular lines meet at a right angle. Parallel lines stay the same distance apart, so they never meet.
Practice questions with worked solutions
Question 1 is free to try. The other 6 open in the free trial, each with its solution film.
What helps with identifying parallel and perpendicular lines in P3?
This first Primary 3 lines lesson builds on the right angle from the Angles chapter.
What your child learns here
This first Primary 3 lines lesson builds on the right angle from the Angles chapter. It teaches your child to recognise perpendicular and parallel lines, check each with a set square or a grid, and name a pair by its letters.
Perpendicular lines meet at a right angle, shown with a small square mark.
Parallel lines stay the same distance apart all along, so they never meet.
Parallel lines can slope; they do not have to go straight across the page.
A line pair is named by letters, for example AB is parallel to CD.
Does the answer make sense?
Parallel lines never meet, so a pair that crosses, or would cross if drawn longer, cannot be the answer to a parallel question. A perpendicular pair must meet at a corner that a set square fits exactly, and a line perpendicular to two others tells your child those two are parallel.
How to practise these questions
The Basic questions practise recognising parallel and perpendicular lines in simple diagrams. The Intermediate questions add naming pairs of lines by their letters in figures that contain several lines. If naming line pairs stalls, watch that question's solution film and try it again later from Revision. The multiple-choice questions ask which picture shows a pair of parallel or perpendicular lines and which statement about lettered lines in a figure is true at Basic, while the Intermediate ones add lines that almost run side by side or cross at a slant; all are solved in writing, without a film.
Questions parents ask
What is the difference between parallel and perpendicular lines? Perpendicular lines meet at a right angle. Parallel lines run in the same direction and stay the same distance apart, so they never meet however far they are drawn.
Do parallel lines have to be the same length? No. Two parallel lines can be any lengths. What makes them parallel is that the gap between them stays the same.
What do the small marks on lines mean? A small square at a corner shows a right angle, so the lines are perpendicular. Matching arrows on two lines show that they are parallel.
