9-3 Area of Parallelograms

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Lesson PresentationLesson Presentation

Problem of the DayProblem of the Day

Lesson QuizzesLesson Quizzes

9-3 Area of Parallelograms

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

9-3 Area of Parallelograms

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

9-3 Area of Parallelograms

Learn to find the area of rectangles and other parallelograms.

9-3 Area of Parallelograms

Vocabulary

area

9-3 Area of Parallelograms

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.

9-3 Area of Parallelograms

Find the area of the rectangle.

Example 1: Finding the Area of a Rectangle

4.5 in.

7.4 in.

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.

9-3 Area of Parallelograms

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 1

9-3 Area of Parallelograms

The area of a playing field is 1,470 ft2 and the length is 42 ft. What is the width of the field?

Example 2: Finding Length or Width of a Rectangle

A = lw

1,470 = 42 · w

=

The width of the playing field is 35 ft.

Use the formula for the area of a rectangle.

Substitute 1,470 for A and 42 for l.

Divide both sides by 42 to isolate w.1,47042

42 · w 42

35 = w

9-3 Area of Parallelograms

The area of a rectangular parking lot is 3,570 ft2 and the width is 70 ft. What is the length of the parking lot?

Check It Out: Example 2

A = lw

3,570 = l · 70

=

The length of the parking lot is 51 ft.

Use the formula for the area of a rectangle.

Substitute 3,570 for A and 70 for w.

Divide both sides by 70 to isolate w.3,57070

70 · w 70

51 = l

9-3 Area of Parallelograms

9-3 Area of Parallelograms

Find the area of the parallelogram.

Example 3: Finding the Area of a Parallelogram

8 m

16 m

A = bh

A = 16· 8

A = 128

The area of the parallelogram is128 m2.

9-3 Area of Parallelograms

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 3

9-3 Area of Parallelograms

A carpenter is laying a wood floor measuring 4 yd by 5 yd. How many square feet of flooring material does she need?

Example 4: Measurement Application

First draw and label a diagram. Look at the units. The wood floor is measured in yards, but the answer should be in square feet.

Convert yards to feet by using a conversion factor.

4 yd

5 yd

9-3 Area of Parallelograms

Example 4 Continued...

Now find the area in square feet.

A = lwUse the formula for the area of a rectangle.

A = 15 · 12 Substitute 15 for l and 12 for w.

A = 180 Multiply.

She needs 180 ft2 of flooring material.

9-3 Area of Parallelograms

A carpenter is laying a wood floor measuring 6 yd by 8 yd. How many square feet of flooring material does he need?

Check It Out: Example 4

First draw and label a diagram. Look at the units. The wood floor is measured in yards, but the answer should be in square feet.

Convert yards to feet by using a conversion factor.

6 yd

8 yd

9-3 Area of Parallelograms

Check It Out: Example 4 Continued...

Now find the area in square feet.

A = lwUse the formula for the area of a rectangle.

A = 24 · 18 Substitute 24 for l and 18 for w.

A = 432 Multiply.

He needs 432 ft2 of flooring material.

9-3 Area of Parallelograms

Standard Lesson Quiz

Lesson Quizzes

Lesson Quiz for Student Response Systems

9-3 Area of Parallelograms

Lesson Quiz: Part I

Find the area of each figure.

1. 2.

3.

24.5 ft2

84 ft2

4.

1318

in2105 8 or

28 12

ft2

572

or

9-3 Area of Parallelograms

Lesson Quiz: Part II

5. Diego is building a rectangular platform measuring 36 in. by 54 in. What is the area of the platform in square feet?

13.5 ft2

9-3 Area of Parallelograms

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

9-3 Area of Parallelograms

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

9-3 Area of Parallelograms

3. Marcheline is building a wooden deck measuring 192 in. by 144 in. What is the area of the platform in square feet?

A. 192 ft2

B. 27,648 in2

C. 28 ft2

D. 32 ft2

Lesson Quiz for Student Response Systems