Suppose oil spills from a ruptured tanker and spreads in a circular pattern. If the radius of the oil spill increases at a constant rate of 2 m/s, exactly how fast (in m2/s) is the area of the spill increasing when the radius is 39 m?

Explanation:

The area of a circle of radius r is given by

Taking the derivative of A with respect to time t, we get

We also know that

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