Year 5 - Maths
Use the terms acute, obtuse and reflex when comparing angles to a right angle
Angles: compare, name, estimate and measure angles
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit pupils will compare the size of angles where there is a clear visual difference and use the terms acute, obtuse and reflex when describing the size of angles or amount of rotation with relation to right angles using a unit called degrees.
Lesson Summary
You will learn to use the terms acute, obtuse and reflex when comparing angles to a right angle.
Key Notes
- Angles are marked with a curve between the lines which have been rotated
- Angles with a bigger turn are larger than those with a smaller turn
- Angles can be bigger than a right ange or smaller than a right angle
Vocabulary To Learn
- Angle: An angle is a measure of turn. It shows how far something has rotated.
- Right angle: A right angle is a square corner or a quarter turn.
- Acute angle: An angle that is smaller than a right angle is an acute angle.
- Obtuse angle: An angle that is greater than a right angle but smaller than a straight line is an obtuse angle.
- Reflex angle: An angle that is greater than a straight line up to a full turn is a reflex angle.
Common Mistakes To Avoid
- Angles must always be formed with one horizontal line. Angles must also have two straight lines that are exactly the same length.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Angles are marked with a curve between the lines which have been rotated. Angles with a bigger turn are larger than those with a smaller turn.
2. Use this key word in a maths sentence and explain it clearly. 'Angle'
An angle is a measure of turn. It shows how far something has rotated. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Angles must always be formed with one horizontal line. Angles must also have two straight lines that are exactly the same length. Correction: Provide pupils with examples where acute, obtuse and reflex angles are shown in a wide range of orientations and where the length of the lines leading into the angles differ in size to support generalising the features of each angle type.
More Lessons In This Unit
- Angles in quadrilaterals Study Guide
- Angles in triangles Study Guide
- Describe rotations using the standard unit of degrees when compared to a right angle Study Guide
- Describe static angles using the standard unit of degrees when compared to a right angle Study Guide
- Draw angles accurately using a protractor Study Guide
- Estimate acute and obtuse angles using the standard unit of degrees Study Guide
- Know that the angles at a point sum to 360 degrees and use this to solve problems Study Guide
- Know that the angles in a full turn sum to 360 degrees and use this to solve problems Study Guide
- Know that the angles on a straight line sum to 180 degrees and use this to solve problems Study Guide
- Measure the size of angles accurately using a protractor Study Guide
- Reasoning about angles in polygons Study Guide
- Review understanding and identification of right angles Study Guide
- Review understanding of angles as a measure of turn Study Guide
- Use the unit of degrees as a standard unit to measure angles Study Guide
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