1. Lesson Presentation:
Notes Page 45
Lesson Quizzes

2. Warm Up
1. What is the perimeter of a square with side lengths of 15 in.?
2. What is the perimeter of a rectangle with length 16 cm and width 11 cm?
60 in.
54 cm

3. The area of a figure is the amount of surface it covers
The area of a figure is the amount of surface it covers. We measure area in square units.

5. Example 1: Finding the Area of a Rectangle
Find the area of the figure.
A = lw
15 in.
Write the formula.
A = 15 • 9
9 in.
Substitute 15 for l.
Substitute 9 for w.
A = 135
The area is about 135 in2.

6. Example 2
Find the area of the figure.
A = lw
Write the formula.
13 in.
A = 13 • 7
7 in.
Substitute 13 for l.
Substitute 7 for w.
A = 91
The area is about 91 in2.

7. You can use the formula for the area of a rectangle to write a formula for the area of a parallelogram. Imagine cutting off the triangle drawn in the parallelogram and sliding it to the right to form a rectangle.
The area of a parallelogram = bh The area of a rectangle = lw.
The base of the parallelogram is the length of the rectangle. The height of the parallelogram is the width of the rectangle.

8. Example 3: Finding the Area of a Parallelogram
Find the area of the parallelogram.
A = bh
Write the formula.
Substitute 2 for b
and 1 for h. 1 2 __ 4 1
A = 2 • 1 1 2 __ 4
1 ft 4 1
2 ft
A = • 5 2 __ 4 2
Multiply.
A = or 3 25 8
___ 1 __
The area is 3 ft2. 1 8 __

9. Example 4
Find the area of the parallelogram.
A = bh
Write the formula. 1
3 ft 2
A = 1 • 3 1 2 __
Substitute 1 for b
and 3 for h. 1 2 __ 1
1 ft 2
A = • 3 2 __ 7
Multiply.
A = or 5 21 4
___ 1 __
The area is 5 ft2. 1 4 __

10. Additional Example 4: Recreation Application
Jessika is going to tile a kitchen that measures 13 ft by 17 ft. Some floor space is taken up by an island that measures 3 ft by 6 ft. How much area remains to be tiled in the kitchen?
To find the area to be tiled, subtract the area of the island from the area of the floor.
floor area –
island =
kitchen area to be tiled
Substitute for l and w in A = lw.
(13 • 17)‏ –
(3 • 6)‏ = n
– = 203
Use the order of operations.
The area of the kitchen to be tiled is 203 ft2.

11. Check It Out: Example 4
Miguel is going to landscape his backyard that measures 16 ft by 11 ft. Some of the backyard space is taken up by a built-in BBQ that measures 2 ft by 4 ft. How much area remains to be landscaped?
To find the landscaped area, subtract the area of the BBQ from the area of the backyard.
backyard area –
BBQ =
landscaped area
Substitute for l and w in A = lw.
(16 • 11)‏ –
(2 • 4)‏ = n
– =
Use the order of operations.
The area of the backyard to be landscaped is 168 ft2.

12. Additional Example 5: Estimating the Area of an Irregular Figure
Find the area of the rectangle.
Count full squares: 19 red squares.
Count almost-full squares: 9 blue squares.
Count squares that are about half- full: 4 green squares = 2 full squares.
Do not count almost empty yellow squares.
Add = 30
The area of the figure is about 30 mi . 2

13. Estimate the area of the figure.
Check It Out: Example 5a
Estimate the area of the figure.
Count full squares: 11 red squares.
Count almost-full squares: 5 green squares.
Count squares that are about half- full: 4 blue squares = 2 full squares.
= mi2
Do not count almost empty yellow squares.
Add = 18
The area of the figure is about 18 mi2.

14. Lesson Quizzes
Standard Lesson Quiz
Lesson Quiz for Student Response Systems

15. Lesson Quiz
Find the area of each figure.
3. What is the area of a parallelogram with base 16 in. and height 10 in.?
4. A square fish pond that is 6 ft long is surrounded by a square walk that is 18 ft long. What is the area covered by the walk?
41.4 m2
48 ft2
160 in2
288 ft2

16. Lesson Quiz for Student Response Systems
1. Find the area of the figure.
A m B m2
C m2 D m2

17. Lesson Quiz for Student Response Systems
2. Find the area of the figure.
A. 60 ft B. 70 ft2
C. 80 ft2 D. 90 ft2

18. Lesson Quiz for Student Response Systems
3. Find the area of a parallelogram with base 19 ft and height 11 ft.
A. 209 ft B. 214 ft2
C. 216 ft2 D. 220 ft2