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Circles (Unit 8). AC DR Area Circumference Diameter Radius. Circles (Unit 8). Video – Learn Alberta. http://www.learnalberta.ca/content/mejhm/index.html ?l=0&ID1=AB.MATH.JR.SHAP&ID2=AB.MATH.JR.SHAP.CIRC&lesson=html/ video_interactives/circles/circlesSmall.html.

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Circles(Unit 8)


AC DR

Area Circumference Diameter Radius


Circles(Unit 8)

  • Video – Learn Alberta

  • http://www.learnalberta.ca/content/mejhm/index.html

  • ?l=0&ID1=AB.MATH.JR.SHAP&ID2=AB.MATH.JR.SHAP.CIRC&lesson=html/

  • video_interactives/circles/circlesSmall.html


Construct Circles(Unit 8)

Student outcome: I will be able to describe the relationship of radius, diameter and circumference

  • Use your compass to draw a circle…Use a ruler to find your radius first!

Radius

Distance from the centre of the circle to the outside edge…represented by “r”

Diameter

Distance across a circle through its centre…represented by “d”


Construct Circles(Unit 8)

Student Outcome: I will be able to describe the relationship between radius, diameter and circumference

  • Question…

  • How can you find the diameter if you are given the radius?

d = r x 2


Construct Circles(Unit 8)

Student Outcome: I will be able to describe the relationship between radius, diameter

  • Question…

  • How can you find the radius if you are given the diameter?

r = d ÷ 2


Let’s Construct Circles

  • Can you design the Olympic rings using a compass??


Let’s Construct Circles

  • Can you design the Olympic rings using a compass??

Rubric – Olympic Rings Rubric – Olympic rings

5 exact rings /5 5 exact rings /5

Parallel /2 Parallel /2

Straight Lines /3 Straight Lines /3

Spacing /Overlap /3 Spacing/Overlap /3

Neatness /2 Neatness /2

Total /15 Total /15


Practice (Homework)

  • Page 271:

  • 5c, 8c, 10, 11, 14

    8ab 5c, 6c, 7c, 8c, 10, 11

    5a, 6, 7, 8b, 10


Circumference of a Circle

Student outcome: I will understand radius, diameter, circumference relationships.

  • Circumference: is the distance (perimeter) around a circle.

Find The Circumference of Objects!

  • What is the relationship between the diameter and circumference of a circle?


Circumference of a Circle

Student outcome: I will be able to describe the relationship of radius, diameter and circumference

  • Circumference: is the distance (perimeter) around a circle.

  • Steps:

  • Wrap a piece of string around the objects circumference

  • Then measure the string along the side of a metre stick.

  • Then measure the diameter of your object and relate it to the circumference.

Find The Circumference of Objects!


Circumference of a Circle

Student outcome: I will understand radius, diameter, circumference relationships.

  • Circumference: is the distance (perimeter) around a circle.

  • What is the relationship between the diameter and circumference of a circle?

  • ∏ is very close to 3 (friendly number)

C = 3 x d (estimated)

C = ∏ x d (actual)

  • The “∏” is known as pi and is known as 3.14

http://www.learnalberta.ca/content/memg/index.html?term=Division03/Circumference/index.html


Circumference of a Circle

Student outcome: I will understand radius, diameter, circumference relationships

  • Circumference: is the distance (perimeter) around a circle.

  • The “∏” is known as pi and is known as 3.14


Circumference of a Circle

Student outcome: I will understand radius, diameter, circumference relationships

  • Circumference: is the distance (perimeter) around a circle.


Circumference of a Circle

Student outcome: I will understand radius, diameter, circumference relationships

  • Circumference: is the distance (perimeter) around a circle.

  • The “∏” is known as pi and is known as 3.14


Show Me What You Know# 1

  • The “∏” is known as pi and is known as 3.14


Circumference of a Circle

  • Did you KNOW?

  • The traditional Plains Indian powwow is an annual

  • celebration. People gather together for storytelling, singing,

  • dancing and feasting. The powwow grounds are circles and

  • the performers dance around the circle in a clockwise

  • direction. How would you determine the distance a dancer

  • travels in one complete trip around the circle?


Circumference of a Circle

Student outcome: I will understand radius, diameter, circumference relationships

  • PROBLEM:

  • What if you were given the “radius.” Then how would you find

  • the circumference? (Remember...before we multiplied the diameter by 3)

  • The “∏” is known as pi and is known as 3.14


Practice (Homework)

  • Page 278-279:

  • 2, 15, 16, 18, 19

    10 2, 3a, 6, 11, 12, 13

    1, 2, 3a, 5, 6, 7a, 9


Secret to the perfect pancake is discovered

http://phys.org/news/2014-03-secret-pancake.html#ajTabs


Practical Quiz #2

  • Using a compass, design a 3 level (snowball) snowman.

  • One snowball has a radius of 2 cm

  • One snowball has a radius of 3 cm

  • One snowball has a diameter of 3 cm


Areaof a Circle

Area means the total amount of space inside of a circle (or any shape).

  • Try to come up with an equation for a circle using the hints given...

  • What are the hints?

5 m


Areaof a Circle

Area Equation is…

Answer is…there are roughly 3 squares (l x w) that fit into a circles. The remaining area outside of the circles roughly make up the area in the 4th part of the circle.

Actual Area Equation:

Area = ∏r ²

5 m


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