# Finding the sum of interior angles in a polygon

In this lesson, we will calculate the sum of interior angles in polygons, and apply this to find missing angles.

This quiz includes images that don't have any alt text - please contact your teacher who should be able to help you with an audio description.

Quiz:

# Intro quiz - Recap from previous lesson

Before we start this lesson, let’s see what you can remember from this topic. Here’s a quick quiz!

Q1.What is the sum of exterior angles of any polygon?

1/5

Q2.Calculate the size of angle a.

2/5

Q3.Calculate the size of angle b.

3/5

Q4.What is the size of each exterior angle of a regular 15 sided polygon?

4/5

Q5.A regular polygon has an exterior angle of 30º. How many sides does it have?

5/5

This quiz includes images that don't have any alt text - please contact your teacher who should be able to help you with an audio description.

Quiz:

# Intro quiz - Recap from previous lesson

Before we start this lesson, let’s see what you can remember from this topic. Here’s a quick quiz!

Q1.What is the sum of exterior angles of any polygon?

1/5

Q2.Calculate the size of angle a.

2/5

Q3.Calculate the size of angle b.

3/5

Q4.What is the size of each exterior angle of a regular 15 sided polygon?

4/5

Q5.A regular polygon has an exterior angle of 30º. How many sides does it have?

5/5

# Video

Click on the play button to start the video. If your teacher asks you to pause the video and look at the worksheet you should:

• Click "Close Video"
• Click "Next" to view the activity

Your video will re-appear on the next page, and will stay paused in the right place.

# Worksheet

These slides will take you through some tasks for the lesson. If you need to re-play the video, click the ‘Resume Video’ icon. If you are asked to add answers to the slides, first download or print out the worksheet. Once you have finished all the tasks, click ‘Next’ below.

This quiz includes images that don't have any alt text - please contact your teacher who should be able to help you with an audio description.

Quiz:

# Finding the Sum of Interior Angles

Don’t worry if you get a question wrong! Forgetting is an important step in learning. We will recap next lesson.

Q1.What is the sum of interior angles of a 20-sided shape?

1/4

Q2.What is the sum of interior angles of a 9-sided shape?

2/4

Q3.What is the missing angle, labelled x?

3/4

Q4.What is the size of each interior angle in a regular octagon?

4/4

This quiz includes images that don't have any alt text - please contact your teacher who should be able to help you with an audio description.

Quiz:

# Finding the Sum of Interior Angles

Don’t worry if you get a question wrong! Forgetting is an important step in learning. We will recap next lesson.

Q1.What is the sum of interior angles of a 20-sided shape?

1/4

Q2.What is the sum of interior angles of a 9-sided shape?

2/4

Q3.What is the missing angle, labelled x?

3/4

Q4.What is the size of each interior angle in a regular octagon?

4/4

# Lesson summary: Finding the sum of interior angles in a polygon

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## Time to move!

Did you know that exercise helps your concentration and ability to learn?

For 5 mins...

Move around:
Climb stairs

On the spot:
Chair yoga