Calculate Angles on a Straight Line

In this activity, we are going to look at angles on a straight line.

You will be using written methods for adding and subtracting.

 

 

As you know, when we complete 1 full turn we move through 360^o  

A straight line is a half turn, so is therefore, half of 360^o

 

You can see this if you look at a protractor.

 

 

Key Point (*Make a note of this)

Angles on a straight line add up to 180°

 

How would we use this information?

 

As with the angles at a point, it means that if we are given the sizes of some angles, we can use this fact to find missing angles.

 

Let's look at an example

Find the missing angle B

 

 

Answer

The angles on a straight line add up to 180° 

B = 180 - 150

B = 30°

 

 

This is what it would look like on the protractor.

 

Let's try some of these!