# Internal angles in a quadrilateral

## Lesson details

### Key learning points

1. In this lesson, we will be able to use triangles to deduce the sum of the interior angles in a quadrilateral. We will also be able to find unknown angles in quadrilaterals.

### 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.
Decide if the following statement is always, sometimes or never true: The diagonals of a quadrilateral intersect.
Always true
Never true
Q2.
Decide if the following statement is always, sometimes or never true: The diagonals of a rhombus are perpendicular.
Never
Sometimes
Q3.
Decide if the following statement is always, sometimes or never true: The diagonals of a trapezium are perpendicular.
Always
Never
Q4.
Decide if the following statement is always, sometimes or never true: The diagonals of a quadrilateral are the same length
Always
Never
Q5.
Which line (A, B or C) is a diagonal of this shape?
A
B
They are all diagonals of the rectangle
Q6.
The diagonals of a three quadrilaterals are shown, draw and name the shapes.
Isosceles trapezium, Kite, Rhombus
Parallelogram, Kite, Delta
Rhombus, Rectangle, Delta

## Exit quiz

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### 6 Questions

Q1.
Find the size of the missing angle.
155 degrees
260 degrees
Q2.
Calculate the missing angle, labelled x
180 degrees
90 degrees
Q3.
Find the missing angles, x, y and z
Correct answer: x = 38, y = 142, z = 142
x = 38, y = 142, z = 38
x = 38, y = 52, z = 142
Q4.
Find the size of the missing angles.
x = 123, y = 100
Correct answer: x = 37, y = 100
x = 68.5, y = 68.5
Q5.
Shown below is a rhombus. Calculate each of the missing angles
They are all diagonals of the rectangle
x = 11.5, y = 141.5, z = 141.5
x = 23, y = 314, z = 314
Correct answer: x = 23, y = 157, z = 157
Q6.
Find the size of the missing angle.