What is the net roof area of a flat roof that measures 40 feet by 20 feet?

To determine the net roof area of a flat roof, one must calculate the area using the formula for the area of a rectangle, which is length multiplied by width. In this scenario, the flat roof has dimensions of 40 feet in length and 20 feet in width.

Applying the formula:

Area = Length × Width Area = 40 feet × 20 feet = 800 square feet

Thus, the net roof area is indeed 800 square feet. This area calculation is crucial for roofing projects as it helps in estimating the amount of material needed, assessing potential drainage issues, and determining costs associated with installation or repairs. The choice reflecting this accurate calculation is the correct answer.