Angles in a triangle

In this lesson, you will understand that the interior angles in a triangle sum to 180°. Solve problems involving unknown angles in triangles.

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 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

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 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

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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:

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

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:

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

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