# Find missing angles when two or more polygons are joined

## Lesson details

### Key learning points

1. In this lesson, we will apply regular polygon knowledge to find missing angles when two or more polygons are joined together.

### 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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### 4 Questions

Q1.
The sum of interior angles of a polygon is 720º. How many sides does the polygon have?
5
7
8
Q2.
The sum of interior angles of a polygon is 2880º. How many sides does the polygon have?
15
16
17
Q3.
The sum of interior angles of a regular polygon is 3960º. What is the size of each interior angle of the regular polygon?
150º
170º
175º
Q4.
The sum of interior angles of a regular polygon is 5040º. What is the size of each exterior angle of the regular polygon?
100.8º
168º
79.2º

## Exit quiz

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### 4 Questions

Q1.
The diagram shows two hexagons joined. Calculate the size of the angle marked b.
144º
60º
90º
Q2.
A regular pentagon and a regular hexagon are joined. Calculate the size of angle a.
105º
117º
144º
Q3.
An octagon and a nonagon are joined. Calculate the size of the angle labelled g.
105º
117º
75º
Q4.
Calculate the size of the angle marked.