A 40 ft by 12 ft CMU wall is built with nominal 8 by 16 face units. Using 1.125 units per square foot and a 5 percent ordering allowance, what unit count should be ordered?
Correct Answer
C) 567 units
Wall area is 40 x 12 = 480 sf. At 1.125 CMU/sf, base quantity is 480 x 1.125 = 540 units. With a 5 percent ordering allowance, 540 x 1.05 = 567 units. Other choices: 540 omits the allowance, 594 uses a 10 percent allowance, and 432 uses one unit per square foot incorrectly.
Why This Is the Correct Answer
Wall area is 40 x 12 = 480 sf. At 1.125 CMU/sf, base quantity is 480 x 1.125 = 540 units. With a 5 percent ordering allowance, 540 x 1.05 = 567 units.
Why the Other Options Are Wrong
Option A: 540 units
cmu quantity, choice a: the answer choice lifts 540 units from the working line.
Option B: 594 units
cmu quantity, choice c: 594 units backs into 528 when divided by 1.125; the accepted setup gives 504 on that same base.
Option D: 432 units
cmu quantity, choice d: 432 units backs into 27 when divided by 16; the accepted setup gives 35.44 on that same base.
Memory Technique
Keep a fastener row beside CMU quantity: if one number is skipped, the option drifts away from 567 units.
Reference Hint
Open Principles and Practices of Commercial Construction, 11th Ed., 2024; use the index entry or section for "Masonry quantity takeoff - CMU face units" to confirm that Wall area is 40 x 12 = 480 sf.
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