Lauretta J. Fox
(figure available in print form)
Any side of a rectangle can be called a base. The altitude to the base, sometimes referred to as the height of the figure, is a segment drawn perpendicular to the base from a point on the opposite side. The lengths of the base and altitude are denoted by b and h respectively. Consecutive sides of a rectangle are perpendicular.
(figure available in print form)
In rectangle ABCD, DC is the base, and AD is the altitude drawn to the base. When each side of the rectangle is divided into unit segments, b = 4 units and h= 2 units. The number of square units contained in the rectangle is eight, or four times two. Thus, the area of the rectangle equals the product of the base and altitude.
Area of a Rectangle = Base x Altitude or A= bh
Example
1: Find the area of a rectangle whose base is 12.5 cm. and whose altitude is 18.6 cm. in length.
Solution
: A- bh A = 12.5 x 18.6 = 232.50 square centimeters
Example
2: Find the area of a rectangle whose base is 9 in. and whose altitude is 3 ft. in length
Solution
: The base and altitude must be represented by the same unit of measure before finding the area. h =3 feet or 3 x 12 = 36 inches
____
Area= bh Area = 9 x 36 = 324 square inches
Example
3: Find the area of the figure on the left below.
(figure available in print form)
Solution
: Divide the figure into rectangles as shown. Find the area of each rectangle. Add the areas of the rectangles to find the total area of the figure.
|
Area I
|
5 x 4
|
= 20 square units
|
|
Area II
|
2 x 3
|
= 6 square units
|
|
Area III
|
12 x 2
|
= 24 square units
|
|
Total Area
|
|
50 square units
|
For practice solve the following problems.
-
1. Find the area of rectangle EFGH with EF = 9.2 mm. and FG = 11.7 mm.
-
2. What is the length of the base of a rectangle whose area is 336 sq. ft. and whose altitude is 14 feet?
-
3. Find the area of a rectangle whose base is 30 yd. and whose diagonal is 34 yd.
-
4. Find the area of a rectangle whose base is 25 yd. and whose altitude is S2 ft.
-
5. Find the cost of painting four rectangular surfaces, each 22 ft. by 15 ft., if 1 gallon of paint will cover 100 sq. ft. and costs $14.95 a gallon.
-
6. Find the areas of the following figures:
(figure available in print form)
