Core TradesQuestion 11 of 700
Six cylindrical concrete piers are each 18 inches in diameter and 4 feet deep. Approximately how many cubic yards of concrete are needed for all six?
a.About 0.8 cubic yards
b.About 1.2 cubic yards
c.About 1.6 cubic yards
d.About 2.4 cubic yards
Explanation
Radius = 9 in = 0.75 ft, so each pier = 3.14 x 0.75^2 x 4 = 7.07 ft^3; six piers = 42.4 ft^3; divided by 27 = about 1.6 cubic yards. The other values result from using the diameter as radius or omitting the pier count.
Law Reference: 2025 CA Building Code (CBC) Chapter 19 (Concrete)Practice all 700 questions free — no signup required.
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