# Related Rates and Differential Equations

(a) If A is the area of a circle with radius r and the circle expands as time passes, find dA/dt in terms of dr/dt.

(b) 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 1 m/s, how fast is the area of the spill increasing when the radius is 30 m?

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#### Solution Preview

(a)

A=Pi*r^2 indicates the area.

Now, to find what we want it suffices to ...

#### Solution Summary

This shows how to find rate of change of area of an oil spill.

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