Perimeter, Circumference,

and AreaGeometryMrs. King

Unit 1, Lesson 7

Rectangles

0Think about this classroom. The floor is a rectangle. 0 If we measured the perimeter, what would that look

like?

0 If we painted the floor, what geometry term are we measuring?

Definitions

Perimeter: the sum of the lengths of the sides of a polygon

Area: the number of square units a polygon encloses

Formulas

Find the perimeter and area of each figure:

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?

P = 4s

P = 4(14) = 56

Because the path is 1 ft wide, increase each side of the garden by 1 ft. s = 1 + 12 + 1 = 14

Extension #1:

Find the area of the figure below.

Step #1: Divide the figure into squares and rectangles:

Extension #2:

AR = bhAR = (15)(5)AR = 75

AS = s2

AS = (5)2

AS = 25

A = 75 + 25 + 25 A = 125

Step #2: Find each area. Then add the areas.

Formulas

C = 2 π (6.5)

C = 13π

C = 13 40.840704 ≈ 40.8

C = 2 π r

⨀ 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.

Example:

A = π r 2

A = π (1.5)2

A = 2.25π

Find the area of ⨀ B in terms of π.

Example:

Homework

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