Lesson Plan 28 - Distributive Property

  1. (5 min) Mental Math
    1. Divide 400 by 100, add 16, then divide by 2 [10]
    2. Multiply 1/2 by 2/3 and reduce your answer [1/3]
    3. What is 20% of 20? [4]
    4. If x - 2 is 10, what is x? [12]
    5. If x is 10, what is 4x + 1? [41]

  2. (10 min) Explain the distributive property:
    • Hand out the distributive property handout
    • Follow the discussion in the handout
    • Use these examples:
      • 2(y + 4) = 2y + 8
      • - 4 (a - 5) = -4a +20 <== don't forget! minus x minus = plus!
      • 5(2a + 3) = 10a + 15
      • - 6(a + 3) = - 6 a - 18
      • (z + 3) 9 = 9z + 27 <== multiplier is behind the parentheses!

    Notice that the distributive law works whether the number (or letter) is in front of or behind the parentheses.

    Here's one more special case:
    X ( 5X + 3 ) = 5X2 + 3X

    because 5X times X = 5 times X2 = 5X2

  3. (Remainder of class) In-class exercise

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