Holt CA Course 1

10-3Area 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

24.5

1823

56 3 or

Holt CA Course 1

10-3Area of Parallelograms

AF3.1 Use variables in expressions describing geometric quantities (e.g.,P = 2w + 2l, A = bh, C = d–the formulas for the perimeter of a rectangle, the area of a triangle, and the circumference of a circle, respectively).Also covered: NS2.1, AF1.1, AF2.1, AF3.2

California Standards

1 2

Holt CA Course 1

10-3Area of Parallelograms

Vocabulary

area

base

height

Holt CA Course 1

10-3Area of Parallelograms

The area of a figure is the number of non-overlapping unit squares needed to cover the figure. Area is measured in square units.

The base of a parallelogram is the length of one side.

Its height is the perpendicular distance from the base to the opposite side.

h

b

Area = 15 square units

Holt CA Course 1

10-3Area of Parallelograms

Holt CA Course 1

10-3Area of Parallelograms

Find the area of the parallelogram.

Finding the Area of a Parallelogram

8 m

16 m

A = bh

A = 16· 8

A = 128

The area of the parallelogram is 128 m2.

Use the formula.

Substitute for b and h.

Multiply.

Holt CA Course 1

10-3Area of Parallelograms

Find the area of the parallelogram.

6 cm

12 cm

A = bh

A = 12· 6

A = 72

The area of the parallelogram is 72 cm2.

Use the formula.

Substitute for b and h.

Multiply.

Holt CA Course 1

10-3Area of Parallelograms

Find the area of the 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.

Holt CA Course 1

10-3Area 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.

Holt CA Course 1

10-3Area of ParallelogramsThe area of a playing field is 1,470 ft2 and the length is 42 ft. What is the width of the field?

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

Holt CA Course 1

10-3Area of ParallelogramsThe area of a rectangular parking lot is 3,570 ft2 and the width is 70 ft. What is the length of the parking lot?

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 l.3,57070

l · 70 70

51 = l

Holt CA Course 1

10-3Area 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?

Step 1: Convert yards to feet.

Step 2: Solve.

4 yd

5 yd

A = l wA= 4 (3) x 5 (3)A= 12 x 15

The carpenter needs 180 ft2 of flooring material.

Holt CA Course 1

10-3Area of Parallelograms

A carpenter is laying a tile floor measuring 5 yd by 7 yd. How many square feet of tile material does she need?

7 (3) x 5 (3) = A

21 x 15 = A

5 yd

7 yd

The carpenter needs 315 ft2 of tile material.

L x W= A

Holt CA Course 1

10-3Area of ParallelogramsLesson Quiz: Part I

Find the area of each figure.

1. 2.

24.5 ft2

4.

1318

in2105 8 or

28 12

ft2

572

=