Lesson Plan # 9 - Intersecting lines, triangle angle measure

  1. (5 min) Mental Math
    1. What is 30 times 3? [90]
    2. What is 30 times 30? [900]
    3. What is 80 times 40? [3200]
    4. What is 90 times 30? [2700]
    5. What is 40 times 60? [2400]

  2. (5 min) Review of selected problems from Homework # 8 (<= 3 problems)
  3. (10 min) Discuss sum of all angles in a triangle:
    1. 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).
    2. Use these examples to show how to compute a missing angle of a triangle, given the other 2 angles:
    3. Distribute "Angle Rules" handout and discuss supplementary angles. Use these examples to show how to compute a supplementary angle given the other angle:
    4. (Remainder of class) In-class Exercise.
    5. Hand out homework as students successfully complete the in-class exercise.