In a comparison of an 8-inch line to a 6-inch line over 500 feet, what is the approximate percent volume reduction?

• A. 56% volume reduction
• B. 30% volume reduction
• C. 44% volume reduction
• D. 22% volume reduction

Answer: (C)

The main idea is that, for pipes of the same length, the volume (or capacity) scales with the cross-sectional area, and for a circular pipe that area is proportional to the square of the diameter. So compare volumes by squaring the diameters.

Compute the volume ratio: V6/V8 = (6^2)/(8^2) = 36/64 = 0.5625. This means the 6-inch line has about 56% of the 8-inch line’s volume. The decrease from 8 inches to 6 inches is 1 − 0.5625 = 0.4375, which is 43.75%, roughly 44%.

So the approximate percent volume reduction is 44%. The other options don’t match this squared-diameter relationship (they’d correspond to the ratio itself rather than the reduction).