The arch is made up of equilateral triangular sections with double walls of steel 3 feet apart. Space between the walls is filled with reinforced concrete. Sizes of the sections vary, but a section at the bottom of the Arch has 54-foot sides and is 12 feet tall. About how much concrete was used between the double walls in one section at the base of the monument?

A triangle with sides s has height s√3/2

So, one section has base area 1/2 (54)(27√3) = 729√3

The volume of concrete is thus 729√3 * 12 = 8748√3 = 15152 ft^3

To find out how much concrete was used between the double walls in one section at the base of the monument, we need to calculate the volume of the space between the walls.

First, let's calculate the volume of the equilateral triangular section. The formula for the volume of a triangular prism is given by:

Volume = (1/2) * Base * Height * Length

In this case, the base length (side length of the equilateral triangle) is 54 feet and the height of the triangular section is 12 feet. The length of the section is the distance between the double walls, which is given as 3 feet. Substituting these values into the formula:

Volume = (1/2) * 54 ft * 12 ft * 3 ft

Next, we need to convert the feet measurement into cubic feet by multiplying the dimensions:

Volume = 0.5 * 54 ft * 12 ft * 3 ft

Simplifying:

Volume = 972 cubic ft

Therefore, approximately 972 cubic feet of concrete was used between the double walls in one section at the base of the monument.