Right angles: less, equal or greater?: what children learn
In this game children sort angles, from clock hands to the corners of shapes, into less than a right angle, a right angle, and greater than a right angle. Comparing each angle with the square corner of a piece of paper is the method to use.
Supports part of Common Core 4.G.A.1: drawing and identifying right angles. 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
- Make a right-angle checker. Fold a piece of paper in half and then in half again. The folded corner is a right angle.
- Compare the angle. Put the checker in the corner of the angle. If the arms match, it is a right angle.
- Less or greater. If the angle fits inside the checker, it is less than a right angle. If it opens wider, it is greater.
- Turns. A quarter turn is one right angle. A half turn is two. A whole turn is four.
Worked examples
Example 1: The angle between clock hands at 3 o'clock
Working: The hands make a square corner.
Answer: a right angle
Example 2: The angle between clock hands at 1 o'clock
Working: The hands are close together, inside the checker.
Answer: less than a right angle
Example 3: The angle between clock hands at 5 o'clock
Working: The hands open wider than a square corner.
Answer: greater than a right angle
Common mistakes and how to fix them
- Judging an angle by the length of its arms. The size of an angle is about the turn between the arms, not how long they are.
- Thinking a right angle must have one arm pointing up. Turn the paper around. A right angle is still a right angle at any rotation.
- Forgetting that a straight line is two right angles. Fold the checker out flat and see that two right angles make a straight line.
Activities to try at home
- Go on a right-angle hunt around the house: doors, books, tiles.
- Use a clock to make right angles with its hands.
- Stand up and make quarter, half and whole turns together.
Ideas for the classroom
- Students make paper right-angle checkers and test angles in the classroom.
- Sort shapes by how many right angles they have.
- Use a geostrip or two rulers to make angles and compare them with a right angle.
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: drawing and identifying right angles. This focused game does not cover the entire standard.
Is a right angle always marked with a square?
Often, yes. A small square in the corner of a shape shows a right angle.
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.