GRE General TestQuantitative ReasoningMedium
A civil engineer is designing a sewage system. A cylindrical pipe has an inner diameter of 0.8 meters and a length of 50 meters. What is the approximate volume of water (in cubic meters) that the pipe can hold when full? (Use π ≈ 3.14)
- A25.12 m³
- B50.24 m³
- C251.2 m³
- D100.48 m³
Show answer & explanationAnswer & explanation
Correct answer: A. 25.12 m³
The volume of a cylinder is calculated using the formula V = πr²h. Given the diameter, first find the radius, then apply the formula.
Why the other options are wrong
- B. This error likely used the diameter (0.8) instead of the radius (0.4) in the r² term, or forgot to square the radius.
- C. This error likely used the diameter (0.8) as radius and squared it, and perhaps an additional multiplication error.
- D. This error likely used the diameter (0.8) as the radius directly in r² or multiplied by 2 somewhere.
Volume of a Cylinder
The volume of a cylinder is the product of the area of its circular base and its height (length).
- Formula: V = πr²h, where r is the radius and h is the height/length.
- Diameter is twice the radius (d = 2r).
- Units for volume are cubic units (e.g., m³).
Memory trick: Cylinder's Volume: Pi-R-Squared-Height, remember to halve the diameter first!