Angles in degrees: what children learn
Year 5 pupils know that angles are measured in degrees. They estimate and compare acute, obtuse and reflex angles, and identify angles at a point and a whole turn (360°), half a turn (180°) and other multiples of 90°.
In this game children sort angles given in degrees into acute, right angle, obtuse and reflex. Knowing the boundaries, 90° and 180°, is all children need to sort any angle.
This topic covers the Year 5 statutory requirement in the National Curriculum in England (Geometry – properties of shapes): pupils should be taught to “know angles are measured in degrees: estimate and compare acute, obtuse and reflex angles”. Year 5 pupils are usually aged 9–10.
For families following US standards, the closest Common Core standard is 4.MD.C.5, which is taught in Grade 4.
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
- Acute: less than 90°. Any angle between 0° and 90° is acute.
- Right angle: exactly 90°. A quarter turn is 90°.
- Obtuse: between 90° and 180°. Wider than a right angle but less than a straight line.
- Reflex: between 180° and 360°. More than a half turn but less than a whole turn.
Worked examples
Example 1: 45°
Working: 45 is less than 90.
Answer: acute
Example 2: 135°
Working: 135 is between 90 and 180.
Answer: obtuse
Example 3: 270°
Working: 270 is between 180 and 360.
Answer: reflex
Common mistakes and how to fix them
- Calling 180° obtuse. 180° is a straight line. Obtuse angles are less than 180°.
- Forgetting reflex angles exist. Look at the outside of an angle: it is reflex if the inside is less than 180°.
- Reading the wrong scale on a protractor. Start from 0 on the arm of the angle and decide first whether the angle is acute or obtuse.
Activities to try at home
- Turn on the spot by 90°, 180°, 270° and 360°.
- Estimate angles in the house and check with a protractor.
- Find out how many degrees the minute hand turns in 15 minutes.
Ideas for the classroom
- Pupils estimate angles before measuring them with a protractor.
- Play 'angle bingo' with angles in degrees.
- Give a set of angles and ask pupils to order them and name each type.
Free printable game and worksheet
The free printable starts with a game sheet, such as a colour-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
Why are there 360 degrees in a whole turn?
It is a very old convention, probably from ancient Babylon. 360 divides by many numbers, which makes it useful.
Do children use a protractor in Year 5?
Yes. Year 5 pupils draw given angles and measure them in degrees.
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.