Parallel and perpendicular lines: what children learn
In this game children sort pairs of lines from everyday objects and shapes into parallel, perpendicular and neither. Parallel lines stay the same distance apart and never meet. Perpendicular lines meet at a right angle.
Supports part of Common Core 4.G.A.1: identifying perpendicular and parallel lines. This focused game does not cover the entire standard.
Common Core connection: 4.G.A.1. This is focused practice for part of the standard.
How to play
Sort the cards into the right groups. Tap a card, then its group. You can also drag a card, or press the number on its group. Each game has 3 rounds with no timer. Every card is checked as soon as you place it: a card in the wrong group comes back with a hint, and you get a point for each card you place right first time. For a quicker go, choose Quick quiz: 10 multiple-choice questions in 150 seconds (choose Relaxed for more time).
Step by step
- Look for the distance between the lines. If the lines stay the same distance apart all the way along, they are parallel.
- Look for a right angle. If the lines meet or cross at a right angle, they are perpendicular.
- Check with a right-angle checker. Use a folded paper corner to test whether lines meet at a right angle.
- Neither. Lines that meet at any other angle are neither parallel nor perpendicular.
Worked examples
Example 1: The two rails of a straight railway track
Working: They stay the same distance apart and never meet.
Answer: parallel
Example 2: The edge of a door and the floor
Working: They meet at a right angle.
Answer: perpendicular
Example 3: The two sloping sides of a triangle's top corner
Working: They meet, but not at a right angle.
Answer: neither
Common mistakes and how to fix them
- Thinking parallel lines must be horizontal. Show parallel lines at a slant, like the sides of a parallelogram.
- Thinking perpendicular lines must cross. Lines that meet at a corner, like an L, are perpendicular too.
- Calling any lines that meet 'perpendicular'. Test the angle with a right-angle checker.
Activities to try at home
- Find parallel and perpendicular lines in the kitchen: tiles, shelves, cupboard doors.
- Look at letters of the alphabet: which have parallel lines and which have perpendicular lines?
- Draw a street map with parallel and perpendicular roads.
Ideas for the classroom
- Students mark parallel lines with arrows and right angles with squares on 2D shapes.
- Use geoboards to make shapes with exactly one pair of parallel sides.
- Sort capital letters into parallel, perpendicular, both and neither.
Free printable game and worksheet
The free printable starts with a game sheet, such as a color-by-answer picture, an answer maze or a secret-code joke, followed by a worksheet. Both use the same checked questions as the online game, and the answers are on the last page. Print it, or save it as a PDF from your browser’s print menu.
Open the free printable game and worksheet
Frequently asked questions
How should I choose this game for my learner?
Supports part of Common Core 4.G.A.1: identifying perpendicular and parallel lines. This focused game does not cover the entire standard.
How are parallel lines marked on a diagram?
With matching small arrows on each line.
Can it be played with a keyboard?
Yes. Tab to a card, press Enter to pick it up, then choose the group it belongs in.