Twelve square concrete columns are each 18 in. by 18 in. and 12 ft tall. Ignoring waste, how much concrete is required?
Correct Answer
D) 12.0 cy
One column contains 1.5 x 1.5 x 12 = 27 cf. Twelve columns contain 324 cf, and 324/27 = 12.0 cy. Other choices: 9.0 cy uses a 15 in. side, 10.5 cy rounds down incorrectly, and 13.5 cy adds waste not requested.
Why This Is the Correct Answer
One column contains 1.5 x 1.5 x 12 = 27 cf. Twelve columns contain 324 cf, and 324/27 = 12.0 cy.
Why the Other Options Are Wrong
Option A: 9.0 cy
column volume, choice a: 9.0 cy is wrong because 9.0 cy equals about 243 cf after cubic-yard conversion; the accepted cubic-foot volume is 27 cf before dividing by 27 in.
Option B: 10.5 cy
column volume, choice b: 10.5 cy equals about 283.5 cf after cubic-yard conversion; the accepted cubic-foot volume is 27 cf before dividing by 27 in.
Option C: 13.5 cy
column volume, choice c: 13.5 cy equals about 364.5 cf after cubic-yard conversion; the accepted cubic-foot volume is 27 cf before dividing by 27 in.
Memory Technique
Picture a dimension string labeled column volume: finish every operation before accepting 12.0 cy.
Reference Hint
Open Principles and Practices of Commercial Construction, 11th Ed., 2024; use the index entry or section for "Concrete quantity takeoff - columns" to confirm that One column contains 1.5 x 1.5 x 12 = 27 cf.
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