How is the drop in inches of a pipe calculated if the grade is known?

To calculate the drop in inches of a pipe when the grade (% slope) is known, the formula involves the relationship between the grade, distance, and how they relate to one another in terms of slope. The correct approach is to take the % slope, divide it by 100 to convert it into a decimal form, and then multiply it by the distance over which the slope is measured. This effectively provides the vertical drop in the same units of measurement.

By applying this method, the formula becomes:

Drop (in inches) = (% slope / 100) * Distance

This calculation directly gives the drop in inches over the specified distance, aligning with standard practices in plumbing and civil engineering. The correct answer captures this relationship accurately, allowing practitioners to determine necessary specifications for installation and compliance with local codes.

The other options do not correctly represent the relationship needed to calculate the drop from the slope and distance: they either misapply the arithmetic operations or misunderstand how to transition from percentage to a usable drop measurement.