# Calculate Angles on Parallel Lines

In this worksheet, students will use angle rules to work out the missing angles in parallel lines.

Key stage:  KS 3

Curriculum topic:   Geometry and Measures

Curriculum subtopic:   Apply the Properties of Angles

Difficulty level:

#### Worksheet Overview

In this activity, we will calculate missing angles in parallel lines.

There are rules we can learn to help us recognise certain angles, which will make it very easy for us!

Make some notes and a quick sketch of each to help you - there are three rules!

1 Alternate angles

These two angles are inside the parallel lines, on the opposite side of the line which crosses.

They form a Z shape.

The angles are the same, so if the top one was 50the alternate one would also be 50o

2 Corresponding

These two angles hang below the parallel lines.

They form an F shape.

They can also be above the parallel lines in an upside down F shape.

The angles are the same, so if the top one was 80the corresponding one would also be 80o

3 Co-Interior

These two angles are inside the parallel lines on the same side of the line crossing.

They form a C shape.

You will notice they are not the same, but they add up to 180o

If the angle C was 80o , then the other co-interior angle D would be 180 - 80 = 100o

Let's try some questions now finding missing angles using these rules!

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