An ellipse watermelon has a major axis 28cm and minor axis 25cm. The equation of the ellipse is y = 12.5 - 12.5x/145

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$\dfrac{x^2}{a^2} + \dfrac{y^2}{b^2} = 1$

assuming the major axis is along the x-axis, $a=14$ and $b=\dfrac{25}{2}$ ...

$\dfrac{x^2}{196}+\dfrac{4y^2}{625} = 1$

$y^2 = \dfrac{625}{4}\left(1-\dfrac{x^2}{196}\right)$

\(\displaystyle V = 2\pi \int_0^{14} \dfrac{625}{4}\left(1-\dfrac{x^2}{196}\right) \, dx\)

\(\displaystyle V = \dfrac{625\pi}{2} \int_0^{14} \left(1-\dfrac{x^2}{196}\right) \, dx = \dfrac{8750\pi}{3}\)