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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.
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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
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Finding the Area of a Circle
The area of a circle can be found using the formula:
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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
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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?
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The Area of a Circle A = πr2 Calculate the area of this shape.
Show all of your working out on your whiteboard.
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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.
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How are the areas of these shapes related?
Can you explain why?
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These shapes have the same areas.
Write possible measurements on your whiteboards
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These shapes have the same areas.
If the radius of circle a is x, what is the diameter of circle b? ? x
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These shapes have the same areas.
If the diameter of circle b is y, what is the radius of circle a? y ?
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The Area of a Circle A = πr2 Calculate of this shape.
Show all of your working out on your whiteboard.
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The Area of a Circle A = πr2 Calculate of this shape.
Show all of your working out on your whiteboard.
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On your whiteboards:
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Title: The area of a circle
Find the areas of these shapes in your books. You must show working out.
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Title: The area of a circle How is area a related to area b? Why?
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Title: The area of a circle How is area b related to area c? Why?
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Title: The area of a circle Can you find some others that are related?
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Title: The area of a circle
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Title: The area of a circle
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