Question

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Answer 1

Answer:
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1)  72$\pi$ cm² / min.  ;
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2)  192 $\pi$ cm² / min.  
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Explanation:
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 Area of a circle:  A = $\pi$ r² ;

Rate of change of Area is:  da/dt = 2$\pi$ r (dr/dt) ;

Given:  dr/dt = 3 cm / min.
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 Problem 1)
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dA/dt = 2 $\pi$ *(12 cm)*(3 cm/ min) = 72 $\pi$  cm² / min. ;
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 Problem 2)
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dA/dt = 2 $\pi$ *(32 cm)*(3 cm/ min) = 192 $\pi$  cm² / min.
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