What is the area of this trapezoid?

A rectangle with a length of 10 and a height of 9 has two right triangles on each side of it with short leg lengths of 9.

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units²

1 answer

To find the area of the trapezoid formed by the rectangular section and the right triangles on each side, we first need to calculate the dimensions of the entire shape.

  1. Calculate the area of the rectangle:

    • The rectangle has a length of 10 and a height of 9.
    • Area of the rectangle = Length × Height = \( 10 \times 9 = 90 \) square units.
  2. Calculate the area of each right triangle:

    • Each right triangle has a short leg (height) of 9 and a base equal to half the length of the rectangle. The base of each triangle would be the same since they are on opposite sides of the rectangle.
    • We need to find that base. Since the trapezoid's longer base is the length of the rectangle, and the triangles' short legs are in line with the rectangle’s height, we have:
      • Base (longer leg of the triangle) = \( \sqrt{(9^2) + (5^2)} = \sqrt{81 + 25} = \sqrt{106} \) (but for the area, we'll use the simpler right triangle area formula).
    • Each triangle is right-angled with the dimensions being 9 (height) and the height of the rectangle being 10.
    • Area of one triangle = \(\frac{1}{2} \times \text{height} \times \text{base} = \frac{1}{2} \times 9 \times 10 = 45\).
  3. Add the areas of the triangles:

    • Since there are two identical triangles, the total area of the triangles = \( 2 \times 45 = 90 \) square units.
  4. Combine the areas to find the total area of the trapezoid:

    • Total Area = Area of Rectangle + Area of Triangles = \( 90 + 90 = 180 \) square units.

Thus, the area of the trapezoid is \( \text{180 units}^2 \).