## Lesson Plan # 12 - Negative Numbers:
multiplication and division:

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- (5 min) Mental Math
- Add 5/8 and 3/8, then reduce [1]
- What is the area of a rectangle whose sides are 6 ft and 11
ft? [66 sq. ft.]
- Start with the number of feet in 8 yards, then divide by the number
of inches in a foot. [2]
- Add 9/16 and 7/16, then reduce. [1]
- Multiply 20 by 30, then divide by 10.[60]

- (5 min) Review of homework #11 (<= 3 problems)

- (15 min) Introduce signed multiplication and division:

- Pass out the "Multiplying and dividing with negative numbers" handout.
Discuss the rules as they are explained in the handout. Go through the
examples on the handout. (Don't do the "2 signs together" part of the
handout discussion).
- Do these examples:
- xy for x = -3, y = +8

- xy for x = +6, y = -5

- ab for a = -5, b = -7

- pq for p = +6, q = +3

- Discuss 2 signs together. Use the second part of the handout
discussion.
- Do these examples (draw circles around the double signs):

- Discuss expression evaluation with parentheses. Explain that things
inside parentheses are performed first. Do these examples:

- a ( b + c ) for a = 3, b = -4, c = +2 = 3 x (-4 + 2) = -6

- 2c ( b - a) for a = -2, b = 3, c = 8 = 16 x (3 + 2) = 80

- ab for a = 1/5 b = 1/3 = 1/5 x 1/3 = 1/15

- 3b for b = 1/3 = 3/1 x 1/3 = 3/3 = 1

- (Remainder of class) In-class Exercise.

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