1. Comparing Perimeter and Area
10-4
Comparing Perimeter and Area
Course 1
Warm Up
Problem of the Day
Lesson Presentation

2. Comparing Perimeter and Area
Course 1
10-4
Comparing Perimeter and Area
Warm Up
1. What is the area of a figure made up of a rectangle with length 12 cm and height 4 cm and a parallelogram with length 12 cm and height 6 cm?
2. What is the area of a figure consisting of a triangle sitting on top of a rectangle? The triangle has a base of 12 in. and height of 9 in., and the rectangle has a base of 12 in. and height of 5 in.
120 cm2
114 in2

3. Comparing Perimeter and Area
Course 1
10-4
Comparing Perimeter and Area
Problem of the Day
If sixteen people sit, evenly spaced, in a circle for story time, who sits directly across from person 5?
person 13

4. Comparing Perimeter and Area
Course 1
10-4
Comparing Perimeter and Area
Learn to make a model to explore how area and perimeter are affected by changes in the dimensions of a figure.

5. Additional Example 1: Changing Dimensions
Course 1
10-4
Comparing Perimeter and Area
Additional Example 1: Changing Dimensions
Find how the perimeter and the area of the figure change when its dimensions change.
= 1 inch
Draw a model of the two figures on graph paper. Label the dimensions.
The original figure is a 4  2 in. rectangle.
The smaller figure is a 2  1 in. rectangle.

6. Additional Example 1 Continued
Course 1
10-4
Comparing Perimeter and Area
Additional Example 1 Continued
Find how the perimeter and the area of the figure change when its dimensions change.
Use the formula for perimeter of a rectangle.
P = 2(l + w)
P = 2(l + w).
Substitute for l and w.
= 2(4 + 2)
= 2(2 + 1)
Simplify.
= 2(6) = 12
= 2(3) = 6
The perimeter is 12 in.
The perimeter is 6 in.

7. Additional Example 1 Continued
Course 1
10-4
Comparing Perimeter and Area
Additional Example 1 Continued
Find how the perimeter and the area of the figure change when its dimensions change.
Use the formula for area of a rectangle.
A = lw
A = lw
Substitute for l and w.
= 4 x 2
= 2 x 1
= 8
Simplify.
= 2
The area is 8 in2.
The area is 2 in2.
The perimeter is divided by 2, and the area is divided by 4.

8. Comparing Perimeter and Area
Course 1
10-4
Comparing Perimeter and Area
Check It Out: Example 1
Find how the perimeter and the area of the figure change when its dimensions change.
= 1 inch
Draw a model of the two figures on graph paper. Label the dimensions.
The original figure is 2 x 2 in. rectangle.
The larger figure is a 4 x 4 in. rectangle.

9. Check It Out: Example 1 Continued
Course 1
10-4
Comparing Perimeter and Area
Check It Out: Example 1 Continued
Find how the perimeter and the area of the figure change when its dimensions change.
Use the formula for perimeter of a rectangle.
P = 2(l + w)
P = 2(l + w).
Substitute for l and w.
= 2(2 + 2)
= 2(4 + 4)
Simplify.
= 2(4) = 8
= 2(8) = 16
The perimeter is 8 in.
The perimeter is 16 in.

10. Check It Out: Example 1 Continued
Course 1
10-4
Comparing Perimeter and Area
Check It Out: Example 1 Continued
Find how the perimeter and the area of the figure change when its dimensions change.
Use the formula for area of a rectangle.
A = lw
A = lw
Substitute for l and w.
= 2 x 2
= 4 x 4
= 4
Simplify.
= 16
The area is 4 in2.
The area is 16 in2.
The perimeter is multiplied by 2, and the area is multiplied by 4.

11. Additional Example 2: Application
Course 1
10-4
Comparing Perimeter and Area
Additional Example 2: Application
Draw a rectangle whose dimensions are 4 times as large as the given rectangle. How do the perimeter and area change?
12 cm
3 cm
8 cm
2 cm
Multiply each dimension by 4.
P = 10 cm
P = 40 cm
A = 6 cm2
A = 96 cm2
When the dimensions of the rectangle are multiplied by 4, the perimeter is multiplied by 4, and the area is multiplied by 16, or 42.

12. Comparing Perimeter and Area
Course 1
10-4
Comparing Perimeter and Area
Check It Out: Example 2
Draw a rectangle whose dimensions are 2 times as large as the given rectangle. How do the perimeter and area change?
10 cm
5 cm
3 cm
6 cm
Multiply each dimension by 2.
P = 16 cm
P = 32 cm
A = 15 cm2
A = 60 cm2
When the dimensions of the rectangle are multiplied by 2, the perimeter is multiplied by 2, and the area is multiplied by 4, or 22.

13. Comparing Perimeter and Area Insert Lesson Title Here
Course 1
10-4
Comparing Perimeter and Area
Insert Lesson Title Here
Lesson Quiz
Find how the perimeter and area of the triangle change when its dimensions change.
The perimeter is multiplied by 2, and the area is multiplied by 4; perimeter = 24, area = 24; perimeter = 48, area = 96.