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8-2 Area of Polygons
Warm UpWarm Up
Lesson PresentationLesson Presentation
Problem of the DayProblem of the Day
Lesson QuizzesLesson Quizzes
8-2 Area of Polygons
Warm UpFind each product.
1. 8 12
2. 3
3. 9.4 6.3
4. 3.5 7
96
59.22
12
513 18 2
3
24.5
8-2 Area of Polygons
Problem of the Day
How many 3 ft by 2 ft rectangles can you cut from one 8 ft by 4 ft rectangle? How much will be left over?
5 pieces; 2 ft2 left over
8-2 Area of Polygons
Prep for MA.7.G.2.1 Justify and use formulas for surface area and volume of pyramids, prisms, cylinders, and cones.Review of MA.6.G.4.3
Sunshine State Standards
8-2 Area of Polygons
Vocabulary
area
8-2 Area of Polygons
The area of a figure is the number of unit squares needed to cover the figure. Area is measured in units of length squared, or square units.
8-2 Area of Polygons
Find the area of the rectangle.
Additional Example 1A: Finding the Area of Rectangles and Parallelograms
A = lw
A = 7.4 · 4.5
A = 33.3
The area of the rectangle is 33.3 in2.
Use the formula.
Substitute for l and w.
Multiply.
8-2 Area of Polygons
Find the area of the parallelogram.
A = bh
A = 16· 8
A = 128
The area of the parallelogram is128 m2.
Additional Example 1B: Finding the Area of Rectangles and Parallelograms
8-2 Area of Polygons
Find the area of the rectangle.
6.3 in.
8.2 in.
A = lw
A = 8.2 · 6.3
A = 51.66
The area of the rectangle is 51.66 in2.
Use the formula.
Substitute for l and w.
Multiply.
Check It Out: Example 1A
8-2 Area of Polygons
Find the area of the parallelogram.
6 cm
12 cm
A = bh
A = 12· 6
A = 72
The area of the parallelogram is72 cm2.
Check It Out: Example 1B
8-2 Area of Polygons
8-2 Area of Polygons
Find the area of the triangle.
Additional Example 2A: Finding the Area of a Triangle
A = 12
bh Use the formula.
A = 12
(8 · 5) Substitute 8 for b and 5 for h.
A = 20
The area of the triangle is 20 square units.
8-2 Area of Polygons
Find the area of the triangle.
Additional Example 2B: Finding the Area of a Triangle
A = 12
bh Use the formula.
A = 12
(9 · 12) Substitute 9 for b and 12 for h.
A = 54
The area of the triangle is 54 square units.
8-2 Area of Polygons
Find the area of the triangle.
A = 12
bh Use the formula.
A = 12
(6 · 9) Substitute 6 for b and 9 for h.
A = 27
The area of the triangle is 27 square units.
Check It Out: Example 2A
6
9
8-2 Area of Polygons
Find the area of the triangle.
A = 12
bh Use the formula.
A = 12
(7 · 10) Substitute 7 for b and 10 for h.
A = 35
The area of the triangle is 35 square units.
Check It Out: Example 2B
10
7
8-2 Area of Polygons
The two parallel sides of a trapezoid are its bases, b1 and b2. The height of a trapezoid is the perpendicular distance between the bases.
8-2 Area of Polygons
In the term b1, the number 1 is called a subscript. It is read as “b-one” or “b sub-one.”
Reading Math
8-2 Area of Polygons
Find the area of the trapezoid.
Additional Example 3A: Finding the Area of a Trapezoid
A = 12
h(b1 + b2) Use the formula.
A = 12
· 6(5 + 9)
A =12
· 6(14)
A = 42
The area of the trapezoid is 42 in2.
Substitute.
Multiply.
Add.
8-2 Area of Polygons
Find the area of the trapezoid.
Additional Example 3B: Finding the Area of a Trapezoid
A = 12
h(b1 + b2) Use the formula.
A = 12
· 7(12 + 16)
A =12
· 7(28)
A = 98
The area of the trapezoid is 98 cm2.
Substitute.
Multiply.
Add.
8-2 Area of Polygons
Find the area of the trapezoid.
A = 12
h(b1 + b2) Use the formula.
A = 12
· 6(11 + 4)
A =12
· 6(15)
A = 45
The area of the trapezoid is 45 in2.
Substitute.
Multiply.
Add.
Check It Out: Example 3A
4 in.6 in.
11 in.
8-2 Area of Polygons
Find the area of the trapezoid.
A = 12
h(b1 + b2) Use the formula.
A = 12
· 9(5 + 16)
A =12
· 9(21)
A = 94.5
The area of the trapezoid is 94.5 cm2.
Substitute.
Multiply.
Add.
Check It Out: Example 3B
16 cm
5 cm
9 cm
8-2 Area of Polygons
Standard Lesson Quiz
Lesson Quizzes
Lesson Quiz for Student Response Systems
8-2 Area of Polygons
Lesson Quiz
Find the area of each figure.
1. 2.
3. 4.
5. 6.
24.5 ft2
45 ft2
28 12
ft2
572
or
9 in2
60 ft2 87.5 ft2
8-2 Area of Polygons
1. Identify the area of the rectangle.
A. 28.09 cm2
B. 28.6 cm2
C. 47.7 cm2
D. 81 cm2
Lesson Quiz for Student Response Systems
9 cm
5.3 cm
8-2 Area of Polygons
2. Identify the area of the parallelogram.
A. 144 in2
B. 72 in2
C. 50 in2
D. 25 in2
Lesson Quiz for Student Response Systems
8-2 Area of Polygons
3. Identify the area of the triangle.
A. 48 cm2
B. 20 cm2
C. 36 cm2
D. 96 cm2
Lesson Quiz for Student Response Systems
