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Use Angle Properties on a Straight Line

In this worksheet, students will learn the rule about angles on a straight line and will use this to find the value of unknown angles using numbers and algebra.

'Use Angle Properties on a Straight Line' worksheet

Key stage:  KS 4

GCSE Subjects:   Maths

GCSE Boards:   AQA, Eduqas, OCR, Pearson Edexcel,

Curriculum topic:   Geometry and Measures, Basic Geometry

Curriculum subtopic:   Properties and Constructions Angles

Difficulty level:  

Worksheet Overview

Angles have various properties or facts which we can use to help us solve related problems.

 

In this activity, we will be investigating and utilising this fact:

Angles on a straight line will always add up to 180°.

 

It is important to note, this condition about the placement of the angles:

Diagram of angles

 

Let's look at this information in practice in some examples now.

 

e.g. Find the missing angle in the diagram below.

Diagram of angles on a straight line

We know that the sum of the angles on the line must add up to 180°

 

Therefore, we can calculate the missing angle by subtracting the known angle from 180:

180° - 45° = 135° 

 

 

That wasn't too tricky, was it? 

 

 

 

Let's try another to check you have the rule down and know how to apply it accurately. 

 

e.g. Find the angle x in the diagram below.

Diagram of angles on a straight line

We might have been given two angles this time, but that is no bother, we just need to follow the same process through twice:

180° - 28° - 53° = 99°

 

Alternatively, we can add the angles given together first and then subtract this total from 180°: 

28° + 53° = 81°

180° - 81° = 99° 

 

 

 

Right then, let's put what we know into action now. 

 

In this activity, we will use the key fact, that angles on a line always add to 180°, to find the value of unknown angles using numbers and algebra and solve problems involving collections of angles. 

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