# Find the number of sides when given the sum of interior angles

In this lesson, we will find the number of sides of a polygon when given only the sum of interior angles.

#### Unit quizzes are being retired in August 2023

Why we're removing unit quizzes from the website >
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 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

#### Unit quizzes are being retired in August 2023

Why we're removing unit quizzes from the website >
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 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

# 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.

#### Unit quizzes are being retired in August 2023

Why we're removing unit quizzes from the website >
Quiz:

# Find the Number of Sides when given 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.The sum of interior angles of a polygon is 720º. How many sides does the polygon have?

1/4

Q2.The sum of interior angles of a polygon is 2880º. How many sides does the polygon have?

2/4

Q3.The sum of interior angles of a regular polygon is 3960º. What is the size of each interior angle of the regular polygon?

3/4

Q4.The sum of interior angles of a regular polygon is 5040º. What is the size of each exterior angle of the regular polygon?

4/4

#### Unit quizzes are being retired in August 2023

Why we're removing unit quizzes from the website >
Quiz:

# Find the Number of Sides when given 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.The sum of interior angles of a polygon is 720º. How many sides does the polygon have?

1/4

Q2.The sum of interior angles of a polygon is 2880º. How many sides does the polygon have?

2/4

Q3.The sum of interior angles of a regular polygon is 3960º. What is the size of each interior angle of the regular polygon?

3/4

Q4.The sum of interior angles of a regular polygon is 5040º. What is the size of each exterior angle of the regular polygon?

4/4

# Lesson summary: Find the number of sides when given the sum of interior angles

## Time to move!

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For 5 mins...

Move around:
Walk

On the spot:
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