Calculate Angles

In this activity, you will need to find missing angles.

 

Missing angles on a straight line:

Angles on a straight line add up to 180°.

To calculate a missing angle on a straight line, take away the known angle from 180°.

 

 

180° - 55° = 125°

 

 

Missing angles in a full turn:

Angles in a full turn add up to 360°.

To calculate a missing angle in a full turn, take away the known angle from 360°.

 

 

360° - 105° = 255°

 

 

Missing angles on intersecting lines:

All 4 angles will add up to 360°.

Opposite angles on a cross are equal.

 

 

360° - 72° - 72° = 216°

216° ÷ 2 = 108°

Both missing angles are 108°

 

 

Missing angles in quadrilaterals:

A quadrilateral is any shape with 4 sides.

For example: square, rhombus, trapezium, parallelogram.

The angles in a quadrilateral add up to to 360°.

 

 

360° - 82° - 82° - 98° = 98°

We can also see that, in this trapezium, opposite angles are the same.