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Grade 7:  The Learning Equation Math

31.01 Circle Measurement

3icon.gif (4368 bytes)


Refresher pp 54-55

Learning Outcomes:

The student will:

Lesson on Circumference of a Circle


circle2.gif (1873 bytes)

r = radius

d = diameter

C = Circumference

p = C/d = 3.14...

source:  Circle Notes


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)



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.



Circle Properties

MathsNet Dynamic Geometry

MathsNet Dynamic Geometry

Math Forum: Squaring the Circle



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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