Topic: Angles E2.3 – Interior Angles of Quadrilaterals

Ontario Curriculum Expectation:

6.E2.3 use the properties of supplementary angles, complementary angles, opposite angles, and interior and exterior angles to solve for unknown angle measures.

Three interior angles of a triangle add up to 180°.

Any quadrilaterals (a shape with 4 sides) can be made up with two triangles.

Since the three interior angles of a triangle adds up to 180°, all the interior angles of a quadrilateral adds up to 360°.

Finding the Unknown Angle

360° = a + b + c + d

360° = 100º + 85º + 90º + d

360° = 275º + d

d = 360° − 275º

d = 85º