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Friday, July 19, 2013

Frustum - Pyramid

Category: Solid Geometry

"Published in Newark, California, USA"

A baking pan has a rectangular base 12 in. by 8 in.; the sides and ends of the pan slope outward, so that the upper edges measure respectively 13 ½ in. by 9 in. Find the volume of a baking pan if the depth of the pan is 2 in. Find the amount of cake batter required to fill the pan to one-half its depth.

Solution:

To illustrate the problem, it is better to draw the figure as follows

Photo by Math Principles in Everyday Life

The area of the upper base is calculated as follows





The area of the lower base is calculated as follows





The volume of a baking pan or a frustum of a pyramid is calculated as follows













If a baking pan is filled with a cake batter one-half of its depth which is 1 in., the volume of a cake batter is calculated as follows


Photo by Math Principles in Everyday Life

The area of the bottom of a baking pan is the same as the bottom of a cake batter which is A2 = 96 in2.

The length of the top of a cake batter is calculated using similar triangles


Photo by Math Principles in Everyday Life













The width of the top of a cake batter is calculated using similar triangles

Photo by Math Principles in Everyday Life







The area of the top of a cake batter is







Therefore, the volume of a cake batter is