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Finding the Area of a Circle

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Presentation on theme: "Finding the Area of a Circle"— Presentation transcript:

1 Finding the Area of a Circle
When finding the areas of other shapes, we used our knowledge of shapes we already knew. For example, to find the area of a parallelogram, we turned it into a rectangle. To find the area of a triangle, we used two triangles to make a parallelogram. To find the area of L-shapes, we partitioned into rectangles.

2 Finding the Area of a Circle
To find the area of a circle, we can partition and rearrange to make a rectangle. Watch this video

3 Finding the Area of a Circle
The area of a circle can be found using the formula:

4 The Area of a Circle A = πr2
Calculate the area of a circle with a radius of 10 using the formula above. Draw a diagram before working it out. How would you type it into your calculator? Calculate the area of a circle with a radius of 20 using the formula above

5 The Area of a Circle A = πr2
Calculate the area of a circle with a diameter of 10 using the formula above. How is this different to the previous questions?

6 The Area of a Circle A = πr2 Calculate the area of this shape.
Show all of your working out on your whiteboard.

7 The Area of a Circle A = πr2 These shapes are not drawn to scale.
Calculate the areas in your books. You must show your working out.

8 How are the areas of these shapes related?
Can you explain why?

9 These shapes have the same areas.
Write possible measurements on your whiteboards

10 These shapes have the same areas.
If the radius of circle a is x, what is the diameter of circle b? ? x

11 These shapes have the same areas.
If the diameter of circle b is y, what is the radius of circle a? y ?

12 The Area of a Circle A = πr2 Calculate of this shape.
Show all of your working out on your whiteboard.

13 The Area of a Circle A = πr2 Calculate of this shape.
Show all of your working out on your whiteboard.

14 On your whiteboards:

15 Title: The area of a circle
Find the areas of these shapes in your books. You must show working out.

16 Title: The area of a circle How is area a related to area b? Why?

17 Title: The area of a circle How is area b related to area c? Why?

18 Title: The area of a circle Can you find some others that are related?

19 Title: The area of a circle

20 Title: The area of a circle


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