1. Angles on Straight Lines

2. What: Sum of angles on straight lines How: Discovering how to measure angles at different points on straight lines Why:

3. A o B

4. 10 20 30 40 50 60 70 80 90

7. A O B

8. A O B

9. A OB

10. Definition: The sum of angles at each point on a straight line is 180 degrees.

11. AB C Harry is trying to work out the sizes of angles A, B and C. Harry thinks : A=100 B=50 C=30 Could Harry be right?

12. Definition: The sum of angles at each point on a straight line is 180 degrees.

13. 120 40 x Find angle x, write your answer on your whiteboard. a)x=20 c) x= 160 b)x=40 d) x=60 Explain why the other answers are wrong

14. Definition: The sum of angles at each point on a straight line is 180 degrees.

15. Harry is putting up some shelves He has made two holes in the wall He measure the angle between the two holes is 200 o Will the shelf be straight?

20. Plenary The sum of angles at each point on a straight line is 180 degrees Easy example Hard example