1. 1 Angles Sum of a Quadrilateral Stage 5 - Year 9 Press Ctrl-A ©2009 – Not to be sold/Free to use

2. 2 Proof The sum of the angles in a quadrilateral is 360 o. Angle Sum of a Quadrilateral

3. 3 A B C A + B + C + D D = 360 o The sum of the angles in a quadrilateral is 360 o. D Angle Sum of a Quadrilateral

4. 4 A+110 o +80 o +120 o = 360 o A + 310 o = 360 o -310 -310 A = 50 o 120 o 80 o 110 o A Example 1 Angle Sum of a Quadrilateral

5. 5 Example 2 110 o 70 o 100 o 2A 2A+110 o +70 o +100 o = 360 o 2A + 280 o = 360 o -280 -280 2A = 80 o A = 40 o ÷2 ÷2 Angle Sum of a Quadrilateral