How many cubic yards of concrete are needed for a rectangular slab that measures 40 feet by 60 feet with a thickness of 6 inches?
Correct Answer
A) 44.4 cubic yards
Volume = 40 ft × 60 ft × 0.5 ft = 1,200 cubic feet. Converting to cubic yards: 1,200 ÷ 27 = 44.4 cubic yards.
Why This Is the Correct Answer
The correct answer is A because the calculation properly converts all measurements to the same units (feet), multiplies length × width × thickness to get cubic feet, then divides by 27 to convert to cubic yards. The 6-inch thickness must be converted to 0.5 feet before calculating. The final result of 44.4 cubic yards represents the exact volume of concrete needed for this rectangular slab.
Why the Other Options Are Wrong
Option B: 48.2 cubic yards
This answer of 48.2 cubic yards is incorrect because it likely results from a calculation error, possibly forgetting to convert the thickness from inches to feet properly or using an incorrect conversion factor between cubic feet and cubic yards.
Option C: 52.6 cubic yards
This answer of 52.6 cubic yards is incorrect and significantly overestimates the concrete needed. This error could result from miscalculating the thickness conversion or using the wrong formula for volume calculation.
Option D: 55.8 cubic yards
This answer of 55.8 cubic yards is incorrect and represents the largest overestimate. This error likely stems from failing to convert inches to feet for the thickness measurement or using an incorrect conversion factor.
Memory Technique
Remember '27 to convert' - there are 27 cubic feet in a cubic yard (3×3×3). For thickness, think 'divide by 12' to convert inches to feet before calculating volume.
Reference Hint
Look up concrete volume calculations and unit conversions in Chapter 3 (Materials and Methods) or the appendix containing conversion tables in your Florida contractor reference manual.
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