(3)

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Step 1:

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The diameter of the inside circle is $\"\"$ .

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The diameter of the outside circle is $\"\"$ .

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The area of the circle is $\"\"$ .

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The area of the inside circle is $\"\"$ .

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Substitute $\"\"$ .

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$\"\"$

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$\"\"$ .

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The area of the outside circle is $\"\"$ .

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Substitute $\"\"$ .

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$\"\"$

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$\"\"$ .

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Step 2:

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The area of the brim is $\"\"$

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Substitute $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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The area of the brim is $\"\"$ .

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Solution:

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The area of the brim is $\"\"$ .