Let be the area of the lower base, the area of the upper base, the area of the midsection, and the altitude. Then as first formulated by Ernst Ferdinand August,
(Kern and Bland 1948, pp. 76-77). This result is known as the prismatoid formula, or sometimes the prismatoid theorem. However, since the latter term is also used for a theorem about the decomposition of a prismatoid (Kern and Bland 1948, pp. 121-130), the term "theorem" is best not applied to the formula.
Alsina, C. and Nelsen, R. B. A Mathematical Space Odyssey: Solid Geometry in the 21st Century. Providence, RI: Math. Assoc. Amer., p. 85, 2015.Beyer, W. H. CRC Standard Mathematical Tables, 28th ed. Boca Raton, FL: CRC Press, pp. 128 and 132, 1987.Halsted, G. B. Rational Geometry: A Textbook for the Science of Space. Based on Hilbert's Foundations, 2nd ed. New York: Wiley, 1907.Harris, J. W. and Stocker, H. "Prismoid, Prismatoid." §4.5.1 in Handbook of Mathematics and Computational Science. New York: Springer-Verlag, p. 102, 1998.Kern, W. F. and Bland, J. R. "Prismatoid," "Prismatoid Theorem," "Proof of the Prismoidal Formula," and "Application of Prismatoid Theorem." §30 and 43-45 in Solid Mensuration with Proofs, 2nd ed. New York: Wiley, pp. 75-80 and 121-130, 1948.Meserve, B. E. and Pingry, R. E. "Some Notes on the Prismoidal Formula." Math. Teacher45, 257-263, 1952.Welchons, A. M.; Krickenberger, W. R.; and Pearson, H. R. Solid Geometry. Boston: Ginn, pp. 274-275, 1959.
be the area of the lower base, 
the area of the upper base, 
the area of the midsection, and 
the altitude. Then as first formulated by Ernst Ferdinand August, 
