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Circles(Unit 8)

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

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

- 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

- 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

- 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

- 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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