1. Area and Perimeter 5-1A What does the area of a figure measure?
What does the perimeter of a figure measure?

2. Definition
They wanted to know the area of the lot before they built their house.
He measured the room and then figured the area of the floor for the new carpet.
Area: the number of square units contained in a plane region. 1 2 3 4 5 6 7 8

3. Remember… Area Formulas
A =l × w l w
Rectangle—the product of length and width.
Square—a rectangle whose length and width are equal.
Triangle—one half the product of the length of the base and the height
A = s2 s
A = ½bh b h

4. Definitions A polygonal region consists of a polygon and its interior.
A polygonal region can always be divided into nonoverlapping triangular regions.
A polygon is a many-sided plane figure whose sides are line segments.

5. Area Postulates
For every polygonal region, there is a unique positive number called the area of the region.
If two polygonal regions are congruent, then they have equal areas.

6. Area Addition Postulate
The area of a polygonal region is the sum of the areas of all of its nonoverlapping parts.
This postulate can help you calculate the areas of complicated regions by breaking the polygonal region down into convenient triangles and rectangles and adding their areas.

7. Find the Area
4 cm
6cm
15 cm
To find the area of the figure, add the area of the rectangle to the area of the triangle.
Rectangle area × 6 = 90 cm2
Triangle area ½(15)(4) = 30 cm2
120 cm2

8. Definition She walked the perimeter of the yard with her dog.
He put a fence on the perimeter of the property.
Perimeter—the distance around the figure.
Perimeter is distance. It is measured in linear units (like inches or centimeters.) To find the perimeter add the length of the sides.

9. Find the Perimeter and Area6 30 10 8 8 10 30 6 20
P = 92
A = 288 21 56
P = 80
A = 400
P = 154
A = 1176

10. What does the area of a figure measure?
The number of square units contained in a plane region.
What does the perimeter of a figure measure?
The distance around the figure.

11. Assignment 5-1A
Worksheet 5-1A