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?

Answer 1

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