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Grade 7:  The Learning Equation Math

31.01 Circle Measurement

3icon.gif (4368 bytes)

Measurement

Refresher pp 54-55

Learning Outcomes:

The student will:

Lesson on Circumference of a Circle

Circumference

circle2.gif (1873 bytes)

r = radius

d = diameter

C = Circumference

p = C/d = 3.14...

source:  Circle Notes

Area

circle_area1.gif (2748 bytes)

C = 2pr

C/2 = pr

The circle (C = 2pr) shown has the area shaded blue and red. Consider the sectors as pieces joined on the circumference, able to be opened out in the two halves. By inter-weaving the sectors, we get the picture shown below where:
  • the base of the parallelogram is half of the circumference (pr)
  • and the height is the radius (r)

base(b)

parallelogram

A = bh

circle_area.gif (3586 bytes)

height(h) = r

 

A = bh = pr(r) =  pr2

Source:  Lesson Plan - Area of a circle

 

Drag the handle to change the size of the radius and diameter. Study the change in circumference and area as you do so.

 

Radius:
Diameter:
Circumference:
Area:
Review:

Circle Properties

MathsNet Dynamic Geometry

MathsNet Dynamic Geometry

Math Forum: Squaring the Circle

 

Enrichment:

The Expanding Circle

9 Point Circle

Constant Perimeter and Area Rectangles

 

Key Terms: A-E F-J K-O P-R S-Z

circle, diameter, radius, circumference, pi, nonrepeating, decimal, polygon

Prerequisite Skills:

Multiplication of Decimals:  Grade 7 Lesson 12.01

Division of Decimals:  Grade 7 Lesson 12.02

Perimeter and Area:   Grade 8 Lesson 32.03

Patterns and Relations:   Grade 7 Lesson 21.02

Linear Equations 1:  Grade 7 Lesson 22.02

Linear Equations 2:  Grade 7 Lesson 22.03

 

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Comments to:  Jim Reed
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