Two parallel sides of a trapezium are 29 cm and 21 cm. Non-parallel sides are equal and each is of length 8.5 cm. What is the area of the trapezium?

  1. A. 187.5 square cm
  2. B. 227.5 square cm
  3. C. 375 square cm
  4. D. 455 square cm

Correct Answer: A. 187.5 square cm

Explanation

Dropping perpendiculars from the shorter parallel side to the longer one creates two identical right triangles with bases \frac{29-21}{2} = 4\text{ cm}. The height h = \sqrt{8.5^2 - 4^2} = \sqrt{72.25 - 16} = 7.5\text{ cm}. The area is \frac{1}{2}(29+21) \times 7.5 = 25 \times 7.5 = 187.5\text{ cm}^2.

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