CSLB General Building (B)Planning and EstimatingMedium
A concrete slab measures 40 feet by 30 feet and will be poured 4 inches thick. Rounding up to the nearest whole cubic yard, how much concrete should be ordered?
- A18 cubic yards
- B15 cubic yards
- C12 cubic yards
- D13 cubic yards
Show answer & explanationAnswer & explanation
Correct answer: B. 15 cubic yards
Convert 4 inches to feet: 4/12 = 0.333 ft. Volume = 40 x 30 x 0.333 = 400 cubic feet. Convert to cubic yards: 400 / 27 = 14.8, which rounds up to 15 cubic yards for ordering purposes.
Why the other options are wrong
- A. This overestimates the volume needed for the slab.
- C. This underestimates the required volume significantly.
- D. This value is too low compared to the correct calculation.
Slab Volume Estimating
Calculating concrete needed for a slab by multiplying length x width x thickness (in feet) to get cubic feet, then converting to cubic yards.
- Always convert thickness in inches to feet first
- 1 cubic yard = 27 cubic feet
- Round up when ordering to avoid running short
Memory trick: Round up your yards so you never run dry.