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
=