Chapter 9 Quadratic Relations and Conic Sections - 9.4 Graph and Write Equations of Ellipses - 9.4 Exercises - Problem Solving - Page 638: 48

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The standard form of an ellipse is $\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$ where $a$ is the length of the major axis and $b$ is the length of the minor axis. Plugging in $a=\frac{81}{2}\\b=6$ we get: $$\frac{x^2}{40.5^2}+\frac{y^2}{6^2}=1\\\frac{x^2}{1640.25}+\frac{y^2}{36}=1$$ Find the area: $V=\pi ab=\pi (\frac{81}{2})(6)\approx763.4 km^2$