HVAC Sheet Metal Block 1 Practice Exam 2026 – Complete Preparation Guide

To determine the amount of material required to fabricate a duct with specified dimensions, we first need to calculate the surface area of the duct. In the provided scenario, the duct has a rectangular cross-section with dimensions of 20 inches by 14 inches and a finished length of 42 inches (which needs to be converted to feet for the final area calculation).

First, let's convert the length from inches to feet:

42 inches ÷ 12 inches/foot = 3.5 feet.

Now, we calculate the perimeter of the duct's cross-section, which is important for determining the area of the material required. The perimeter of a rectangle is calculated by the formula:

Perimeter = 2 * (width + height).

For this duct:

Width = 20 inches,

Height = 14 inches.

Calculating the perimeter:

Perimeter = 2 * (20 inches + 14 inches) = 2 * 34 inches = 68 inches.

Next, we calculate the surface area of the duct's sides. The surface area is determined by multiplying the perimeter by the length of the duct:

Surface Area = Perimeter * Length.

First, we convert the perimeter from inches to feet for compatibility with the length:

68 inches ÷