Which calculation represents the area of a trapezoid?

The area of a trapezoid is calculated using the formula that takes the average of the two bases and multiplies it by the height. This is captured in the correct choice, which states to average the two bases by adding them together and dividing by two, then multiplying by the height. Specifically, the two bases of the trapezoid represent the lengths of the parallel sides, while the height is the perpendicular distance between those two bases.

In contrast, the other options involve different calculations that don’t correctly represent the area of a trapezoid. For instance, simply adding the bases and multiplying by the height does not account for the average length of the bases, which is essential for finding the trapezoid's area. The formula that multiplies the bases and divides by the height does not apply to trapezoids, as this approach is more relevant to different geometric calculations. Lastly, the option referring to Base x Height applies specifically to rectangles or squares, where only one base side is relevant. Understanding the geometric principles behind these formulas is key to correctly identifying how to calculate areas for various shapes, including trapezoids.