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How to Determine the Area of a Trapezoid

A trapezoid is a four-sided figure with one pair of parallel sides. Because a trapezoid can be dissected into a rectangle and two identical triangles, find it’s area is easy.


  • Step 1: Sum the length of the two parallel sides Add the lengths of the two parallel sides of the trapezoid.
  • Step 2: Multiply by the height Find the height of the trapezoid. Using a calculator, multiply the sum of the lengths by the height.
  • Step 3: Divide by two Divide the product by two. This is the area of the trapezoid.
  • TIP: For example, if the height of a trapezoid is 20 inches and two parallel sides of the trapezoid measure 13 and 15 inches, the area is given by = ½ × 20 × (13 + 15), or 280 square inches.
  • Step 4: Look for similar examples Be on the lookout for other polygons whose areas can be determined more easily if the polygons are composed of simpler shapes.
  • FACT: The word trapezoid comes from the Greek word for table.

You Will Need

  • The dimensions of the trapezoid
  • A calculator

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