After cutting a circular piece of paper, assemble it into an approximate rectangle whose width is equal to the radius and the area remains constant. The perimeter of this rectangle is 24.84 cm. What is the area of the circular piece of paper before cutting.
把一个圆形纸片剪开后，拼成一个宽等于半径，面积不变的近似长方形，这个长方形的周长是24.84厘米，剪开前的圆纸片的面积是多少．
<gadget id="calculator">1 + 3.14</gadget>
<output>4.14</output>

<gadget id="calculator">24.84 / 2 / 4.14</gadget>
<output>3</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<result>28.26</result>