Question 108777
Make sure you change all of your measurements to inches. 
Diameter of the pillar - 1'9" = 21"
Area of the pillar - {{{A=(pi) D^2}}}
{{{A=(pi) 21^2}}}
{{{A=1385}}}
Length of the pillar - 12'6"=150"
Volume of the pillar - {{{V=AL}}}
{{{V=AL}}}
{{{V=1385*150}}}
{{{V=207816}}}
The volume of one pillar is 207,816 cubic inches. 
The volume of eight pillars is 8(207,816) or 1,662,531 cubic inches. 
Since concrete is measured in cubic yards we need to multiply our number by a conversion factor.
Since {{{1 yd=36 in}}}, then {{{ 1 yd^3=(36^3) in^3=46656 in^3}}}
{{{V=1662531 in^3*((1 yd^3)/(46656 in^3))}}}
{{{V=35.6}}}
35.6 cubic yards of concrete are required for the pillars.