Calculate Missing Angles in Quadrilaterals

In this activity, we will find missing angles in quadrilaterals.

 

Quadrilaterals have four sides and four angles!

 

The total of all the angles in a triangle is 180^o

 

 

As a quadrilateral is made up of two triangles, the angles in a quadrilateral add up to 180 + 180 = 360

 

 

How would we use this in a question?

 

Let's try one .......

 

Example

Find the missing angle A in the quadrilateral.

 

 

Answer

To find angle A, we add up the existing angles and subtract this from 360°.

A = 360 - (70 + 120 + 65)

A = 360 -  255

A  = 105°

 

Does that make sense?

 

 

Let's have a go at some questions.