# Angles in a triangle

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## Lesson details

### Key learning points

- 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.

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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?

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

### 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°

60°

Q6.

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

10°: 20°: 30°

60°:60°:60°

90°:45°:45°