A parallelogram is cut and patched to form a square. The perimeter of the square is 20 cm. What is the area of the parallelogram?
一个平行四边形，把它割补后成为一个正方形，这个正方形的周长是20厘米，这个平行四边形的面积是多少？
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 * 5</gadget>
<output>25</output>

<result>25</result>