Lesson Plan 28 - Distributive Property
- (5 min) Mental Math
- Divide 400 by 100, add 16, then divide by 2 [10]
- Multiply 1/2 by 2/3 and reduce your answer [1/3]
- What is 20% of 20? [4]
- If x - 2 is 10, what is x? [12]
- If x is 10, what is 4x + 1? [41]
- (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
- (Remainder of class) In-class exercise
- Hand out homework as students successfully complete the in-class exercise.
|