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Wednesday, February 20, 2013

Square Pyramid Problems

Category: Solid Geometry, Plane Geometry

"Published in Newark, California, USA"

A vessel is in the form of an inverted regular square pyramid of altitude 9.87 in. and a base edge 6.27 in. The depth of the water it contains is 6 in. How much will the surface rise when 1 pint of water is added? (One gallon = 231 cubic inches) Find the wetted surface when the depth of the water is 9.23 in. 

Solution:

To illustrate the problem, let's draw the figure and label as follows


Photo by Math Principles in Everyday Life

The volume of the empty vessel is calculated as follows









When the depth of the water is 6 in, the volume is calculated by ratio and proportion as follows








When 1 pint of water is added, the volume in cubic inches is







Therefore, after the addition of 1 pint of water, the height of water can be calculated by ratio and proportion as follows











The difference of the height of water after the addition of 1 pint of water is





When the depth of the water is 9.23 in, the length of a square base is calculated by ratio and proportion as follows







By Pythagorean Theorem, the slant height will be equal to


Photo by Math Principles in Everyday Life











Therefore, the wetted surface of a vessel is