GRE General TestQuantitative ReasoningMedium
A civil engineer is calculating the required volume of concrete for a cylindrical pillar. The pillar has a diameter of 3 meters and a height of 4 meters. If concrete costs $120 per cubic meter, what is the total cost of concrete for the pillar? (Use π ≈ 3.14)
- A$4,521.60
- B$2,543.40
- C$3,391.20
- D$4,239.00
Show answer & explanationAnswer & explanation
Correct answer: C. $3,391.20
The radius is diameter/2 = 3/2 = 1.5 meters. Volume of a cylinder = π * r^2 * h = 3.14 * (1.5)^2 * 4 = 3.14 * 2.25 * 4 = 28.26 cubic meters. Total cost = 28.26 * $120 = $3,391.20.
Why the other options are wrong
- A. This is a plausible distractor, possibly from an incorrect volume calculation.
- B. This could be a calculation error or using diameter instead of radius squared.
- D. This is a plausible distractor, perhaps from using diameter directly for radius.
Volume of a Cylinder
The amount of space occupied by a three-dimensional cylindrical shape, calculated using its radius and height.
- Formula: V = π * r^2 * h
- Radius is half the diameter.
- Units are typically cubic (e.g., cubic meters).
Memory trick: Pi R squared H, volume you'll see, then multiply by cost, for total fee!