Lesson Plan # 17 - Introduction to Probability

  1. (5 min) Mental Math
    1. Multiply 1/3 by 3/8 and reduce [1/8]
    2. Start with 125, multiply by 10, then subtract 50 [1200]
    3. What is the perimeter of a rectangle whose sides are 10 feet and 5 feet? [30 feet]
    4. What is the area of a triangle whose base is 8 feet and whose height is 6 feet? [24 sq. ft.]
    5. What is the decimal for 526 divided by 100? [5.26]

  2. (5 min) Review of homework #15 (<= 3 problems)

  3. (10 min) Introduce probability:

    1. Pass out the "Notes on Probability"
    2. Explain that probability has to do with the future. Contrast it to statistics:

      PastFuture
      Statistics about things
      that have already occurred      		 Probability of things
      happening in the future
    3. Define probability as a fraction:
        NUMBER OF THINGS YOU ARE LOOKING FOR
  -------------------------------------
        TOTAL NUMBER OF THINGS
    4. Discuss maximum probability (1), minimum probability (0) and what they mean. Ask students for examples.
    5. Use examples in the handout to illustrate basic probabilities.
      Use these additional examples, if you wish, and ask students to solve them:
      1. Probability of pulling the 6 of hearts out of a deck of 52 cards. [1/52]
      2. Probability of drawing a blue marble out of the bag in the handout [5/7]
      3. Probability of drawing a blue or a red marble out of the bag in the handout [7/7 or 1]


      Note: this discussion goes much better
      if you bring things to illustrate probability
      with you, like dice, cards,coins, or marbles.

      One technique that I have used successfully
      is to spread an entire deck of cards out on
      the floor in a rectangle, with each suit
      being a row. When you then ask students
      for probabilities of drawing certain cards
      or suits, they can see it pictorially
      for themselves.


  4. (Remainder of class) In-class Exercise.

  5. Hand out homework as students successfully complete the in-class exercise.