Use area formulas for rectangles, triangles, parallelograms, trapezoids, and composite figures.
Model a less-regular region with area formulas
Problem
A school orders a trapezoid-shaped banner for the gym. The banner has bases of \(12~\text{feet}\) and \(18~\text{feet}\), and its height is \(7~\text{feet}\). What is the area of the banner in square feet?
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What this problem is really about
A trapezoid’s width changes steadily from one parallel base to the other, so use the average of those base lengths. Multiply that average by the perpendicular height, which is equivalent to taking one-half of the base sum times the height. Including both bases and the one-half factor keeps the setup tied to the entire banner region.
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