SOLUTION: C-12 Construction: How many cubic yards of concrete are needed to pour eight cylindrical pillars 12 ft 6 in high, each with a diameter of l ft 9 in.?

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Question 108777: C-12 Construction: How many cubic yards of concrete are needed to pour eight cylindrical pillars 12 ft 6 in high, each with a diameter of l ft 9 in.?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Make sure you change all of your measurements to inches.
Diameter of the pillar - 1'9" = 21"
Area of the pillar - A=%28pi%29+D%5E2
A=%28pi%29+21%5E2
A=1385
Length of the pillar - 12'6"=150"
Volume of the pillar - V=AL
V=AL
V=1385%2A150
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%5E3=%2836%5E3%29+in%5E3=46656+in%5E3
V=1662531+in%5E3%2A%28%281+yd%5E3%29%2F%2846656+in%5E3%29%29
V=35.6
35.6 cubic yards of concrete are required for the pillars.