## Lesson Plan # 9 - Intersecting lines, triangle
angle measure

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- (5 min) Mental Math
- What is 30 times 3? [90]
- What is 30 times 30? [900]
- What is 80 times 40? [3200]
- What is 90 times 30? [2700]
- What is 40 times 60? [2400]

- (5 min) Review of selected problems from Homework # 8 (<= 3
problems)

- (10 min) Discuss sum of all angles in a triangle:
- Cut up the paper triangle and tape it together with a common
vertex to show that they add up to 180 degrees (a straight line).
- Use these examples to show how to compute a missing
angle of a triangle, given the other 2 angles:

** Distribute "Angle Rules" handout and discuss supplementary
angles. Use these examples to show how to compute a supplementary
angle given the other angle:
****(Remainder of class) In-class Exercise.
**** Hand out homework as students successfully complete the in-class
exercise.
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