# Angles in a triangle

## Lesson details

### Key learning points

1. 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.

### Licence

This content is made available by Oak National Academy Limited and its partners and licensed under Oak’s terms & conditions (Collection 1), except where otherwise stated.

## Video

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## Worksheet

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## Starter quiz

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### 6 Questions

Q1.
What is a triangle with at least two equal sides called?
Equilateral triangle
Obtuse triangle
Scalene triangle
Q2.
What is a triangle with three equal sides called?
Isosceles triangle
None
Scalene triangle
Q3.
Would it be possible to draw a scalene triangle with more than one obtuse angle?
Correct answer: No, this will be impossible
Yes, this will be possible
Q4.
The sum of all the angles of a triangle is:
100 degrees
360 degrees
90 degrees
Q5.
Zaki and Connor are looking at the diagram on the right. Who do you agree with? Why?
Connor
Neither of them
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?
Equilateral triangle
Isosceles triangle

## Exit quiz

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### 6 Questions

Q1.
Grace has measured the three angles in a triangle. Two of her measurements are 48° and 70°. What is the third measurement?
118°
152°
242°
Q2.
Find the size of the missing angle
157
23°
Q3.
Find the missing angle labelled, x
106°
127°
90°
Q4.
Find the missing angle, labelled x
145°
34°
68°
Q5.
Work out the missing angle, labelled x
11°
169°