If there are two equal height prisms, and one has a parallelogram, and the other a triangle, (as a) base, and the parallelogram is double the triangle, then the prisms will be equal. * Let $ABCDEF$ and $GHKLMN$ be two equal height prisms, and let the former have the parallelogram $AF$, and the latter the triangle $GHK$, as a base. * And let parallelogram $AF$ be twice triangle $GHK$. * I say that prism $ABCDEF$ is equal to prism $GHKLMN$.
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