A farmland is in the shape of a rhombus. The perimeter of the land is 100 m and the length of one of the diagonals is 40 m. The land is divided into four equal parts. What is the area of each part?

  1. A. 150 square metre
  2. B. 225 square metre
  3. C. 300 square metre
  4. D. 450 square metre

Correct Answer: A. 150 square metre

Explanation

Perimeter = 100 m implies side = 25 m. The diagonals of a rhombus bisect each other at 90^\circ. One half-diagonal is 20 m. By Pythagoras, the other half-diagonal is \sqrt{25^2 - 20^2} = \sqrt{225} = 15 m. The four equal parts are right triangles formed by the diagonals. Area of one such part = \frac{1}{2} \times 20 \times 15 = 150 square metres.

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