1. Warm Up Problem
Which of the following expressions is equivalent to 6x + 24? A) 3(x + 12) B) 6(x – 4) C) 6(x + 4) D) x(6 + 4)

2. Changes in Dimension
Lesson 9-4

3. Objectives
I can determine the effects of changing the dimensions on perimeter and area. I can explain the difference between the perimeter and the area of a polygon.

5. The perimeter is 3 times bigger.
Example 1
Suppose the side lengths of the parallelogram at the right are tripled. What effects would this have on the perimeter?
Side A
Side B
Perimeter 3 4
= 14 in
Tripled (Multiplied by 3) 9 12
= 42 in
42 ÷ 14 = 3
The perimeter is 3 times bigger.

6. Got It?
1. Suppose the side lengths of the trapezoid at the right are multiplied by What effect would this have on the perimeter?
Top
Side
Bottom
Perimeter 13 14 24
halved

7. Big Idea: square the scale factor (what your multiplying by) be the area.

8. The area is 52 or 25 times bigger.
Example 2
The side lengths of the triangle at the right are multiplied by 5. What effect would this have on the area?
25 ÷ 1 = 25
The area is 52 or 25 times bigger.
Base
Height
Area 2 1
A = ½ (2)(1)
= 1 cm2
Multiplied by 5 10 5
A = ½ (10)(5)
= 25 cm2

9. Got It?
2. A rectangle measures 2 feet by 4 feet. Suppose the side lengths are multiplied by What effect would this have on the area?
Length
Height
Area 2 4
Multiplied by 2.5

10. Example 3
A stop sign is in the shape of a regular octagon. Sign A shown at the right has an area of 309 square inches. What is the area of sign B?
Since 12 ÷ 8= 1.5
The area is 309(1.5²).
309 (2.25) =
695.25in²

11. Got It?
3. Different sizes of regular hexagons are used in a quilt. Each small hexagon has side lengths of 4 inches and an area of 41.6 square inches. Each large hexagon has side lengths of 8 inches. What is the area of each large hexagon? Hint: 8 ÷ 4 = 2, so the large is twice as big as the small.

12. Homework Hints
When is says “Justify your answer” it means to show your work. #5. First, find the width (80 x width = 4800). Then multiply each length (80) and width (?) by the fraction. #6a. In other words, find the area of the triangle shown. #6b. Now, double the base and height and find the area again.