Angles — Tasmanian Year 4 Maths
Naming angles as acute, right, obtuse or straight, then the large angles, reflex angles and revolutions, all compared with a right angle. Two subtopics and 40 questions with answers, aligned to AC9M4M04.
Angles in Tasmanian Year 4
This topic is about how big an angle is, judged by comparing it with a right angle, the square corner of a page. Students name acute, right, obtuse and straight angles, then move on to the large angles, reflex angles and revolutions, and link each angle to an amount of turn. No protractor is needed at this stage.
The two subtopics below are classifying angles as acute, right or obtuse, and straight, reflex and revolution angles. Angles is one of the 20 topics in Tasmanian Year 4 Maths and sits in the Measurement strand. Both subtopics come under Australian Curriculum code AC9M4M04. Measuring angles in degrees comes in later years.
Subtopics
Angles: common questions
What are acute, right and obtuse angles?
A right angle is a square corner, a quarter turn. An acute angle opens less than a right angle, and an obtuse angle opens more than a right angle but less than a straight line. Check with the corner of a sheet of paper: if the angle fits inside the corner, it is acute.
What is a reflex angle?
Reflex angles are bigger than a half turn but smaller than a full turn. Every corner has an inside angle and an outside angle, and when the inside angle is less than a straight angle, the outside one is reflex. At 7 o’clock the clock hands make an obtuse angle on one side and a reflex angle on the other.
Does the length of the arms change the size of an angle?
No. The size of an angle is how far its arms open, not how long they are. Two angles with the same opening are the same size even if one is drawn with much longer arms, which is a common trap when children compare angles by eye.
How can my child practise angles at home?
Go on an angle hunt: right angles in doors and books, acute angles in a slice of pizza and obtuse angles in an open laptop. Use your arms to show quarter, half and full turns, and look at the angles clock hands make at different times of the day.
Which curriculum codes cover Angles in Tasmanian Year 4?
Both subtopics come under Australian Curriculum v9 code AC9M4M04, the Year 4 content on estimating and comparing angles, naming them from acute to revolution, and relating each one to a right angle.