Year 5 - Maths
Angles in triangles
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 know that the angles in a triangle sum to 180°.
Key Notes
- Angles on a straight line sum to 180 degrees.
- Interior angles in triangles sum to 180 degrees.
- Missing angles can be calculated using the sum of 180 degrees.
Vocabulary To Learn
- Quadrilateral: A quadrilateral is a polygon with four straight sides and four vertices.
- Triangle: A triangle is a polygon with three straight sides and three vertices.
- Sum: The sum is the result of adding two or more numbers.
Common Mistakes To Avoid
- Pupils struggle to remember the number of degrees in a triangle as they only know it as a disconnected fact.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Angles on a straight line sum to 180 degrees. Interior angles in triangles sum to 180 degrees.
2. Use this key word in a maths sentence and explain it clearly. 'Quadrilateral'
A quadrilateral is a polygon with four straight sides and four vertices. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils struggle to remember the number of degrees in a triangle as they only know it as a disconnected fact. Correction: Apply pupils' knowledge of angles in a quadrilateral to understanding the sum of the angles in a triangle. Spend time showing how a quadrilateral is constructed using triangles and what happens to the angles as the quadrilateral is partitioned.
More Lessons In This Unit
- Angles in quadrilaterals 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 terms acute, obtuse and reflex when comparing angles to a right angle Study Guide
- Use the unit of degrees as a standard unit to measure angles Study Guide
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