Area of a trapezoid is the average of the two parallel sides times the height. Parallel sides 8 and 14, height 5: ((8 + 14) / 2) × 5 = 55. The full shape list is in area and volume.
Find the parallels
A trapezoid has exactly one pair of parallel sides. Average those two, then multiply by the perpendicular height, not a slanted leg. If the figure is not labeled, drop perpendiculars to make a rectangle and two right triangles, then add the three areas. That is the same number.
Triangles use one-half base times height, in area of a triangle. Right-triangle legs for those drop-downs are in Pythagorean theorem and special right triangles. Formulas as a set are in ACT Math formulas.
The bottom line
Average the parallel sides. Multiply by the perpendicular height.
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