Using angles on a straight line have a sum of 180° students learn how to calculate missing angles and set up and solve simple equations this property. More able students apply this to recognise and calculate vertically opposite angles.

The start of the lesson recaps perpendicular angles. In the main part students learn how to calculate missing angles on a straight line using the sum of 180°. The plenary challenges students to create a straight line out of three known angles.

**Differentiated Learning Objectives**

- All students should be able to know the sum of the angles on a straight line is 180°.
- Most students should be able to calculate vertically opposite angles and angles on a straight line.
- Some students should be able to prove that vertically opposite angles are equal.