<PRE><B>Question 330009</B>
A rock is dropped in a pond and the ripples form circles in the water. if the area of each ripple is increasing at a rate of 20 square centimeters per second, then how fast is the radius changing when the radius is 5 centimeters
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A = pi(r^2)
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dA = 2pi(r)dr
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20 = 2pi(5)dr
dr = 2/pi cm per second
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Cheers,
Stan H.
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