# Angles in a triangle

In this lesson, we will understand that the interior angles in a triangle sum to 180°. We will also solve problems involving unknown angles in triangles.

#### 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 a triangle with at least two equal sides called?

1/6

Q2.What is a triangle with three equal sides called?

2/6

Q3.Would it be possible to draw a scalene triangle with more than one obtuse angle?

3/6

Q4.The sum of all the angles of a triangle is:

4/6

Q5.Zaki and Connor are looking at the diagram on the right. Who do you agree with? Why?

5/6

Q6.I am thinking of a triangle which have the following properties: no lines of symmetry and has one right angle. Which triangle am I thinking of?

6/6

#### 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 a triangle with at least two equal sides called?

1/6

Q2.What is a triangle with three equal sides called?

2/6

Q3.Would it be possible to draw a scalene triangle with more than one obtuse angle?

3/6

Q4.The sum of all the angles of a triangle is:

4/6

Q5.Zaki and Connor are looking at the diagram on the right. Who do you agree with? Why?

5/6

Q6.I am thinking of a triangle which have the following properties: no lines of symmetry and has one right angle. Which triangle am I thinking of?

6/6

# 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:

# Angles in a Triangle

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

Q1.Grace has measured the three angles in a triangle. Two of her measurements are 48° and 70°. What is the third measurement?

1/6

Q2.Find the size of the missing angle

2/6

Q3.Find the missing angle labelled, x

3/6

Q4.Find the missing angle, labelled x

4/6

Q5.Work out the missing angle, labelled x

5/6

Q6.The ratio of three angles in a triangle are 1:2:3. Work out the size of each angle.

6/6

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

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

# Angles in a Triangle

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

Q1.Grace has measured the three angles in a triangle. Two of her measurements are 48° and 70°. What is the third measurement?

1/6

Q2.Find the size of the missing angle

2/6

Q3.Find the missing angle labelled, x

3/6

Q4.Find the missing angle, labelled x

4/6

Q5.Work out the missing angle, labelled x

5/6

Q6.The ratio of three angles in a triangle are 1:2:3. Work out the size of each angle.

6/6

# Lesson summary: Angles in a triangle

## Time to move!

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

For 5 mins...

Move around:
Walk

On the spot:
Chair yoga