1. Perimeter, Circumference, and Area
Geometry
Mrs. King
Unit 1, Lesson 7

2. Rectangles Think about this classroom. The floor is a rectangle.
If we measured the perimeter, what would that look like?
If we painted the floor, what geometry term are we measuring?

3. Definitions
Perimeter: the sum of the lengths of the sides of a polygon Area: the number of square units a polygon encloses

4. Formulas

5. Find the perimeter and area of each figure:

6. Extension #1:
Margaret’s garden is a square 12 ft on each side. Margaret wants a path 1 ft wide around the entire garden. What will the outside perimeter of the path be?
Because the path is 1 ft wide, increase each side of the garden by 1 ft. s = = 14
P = 4s
P = 4(14) = 56

7. Extension #2: Find the area of the figure below.
Step #1: Divide the figure into squares and rectangles:
Step #2: Find each area. Then add the areas.
AR = bh
AR = (15)(5)
AR = 75
AS = s2
AS = (5)2
AS = 25
A =
A = 125

8. Formulas

9. Example:
⨀ G has a radius of 6.5 cm. Find the circumference of ⨀ G in terms of π. Then find the circumference to the nearest tenth.
C = 2 π r
C = 2 π (6.5)
C = 13π
C = ≈ 40.8

10. Example: Find the area of ⨀ B in terms of π. A = π r 2 A = π (1.5)2

11. Homework Perimeter, Circumference, and Area in Student Practice Packet
(Page 8, #1-16)