Divide a circle into several sectors and cut them into a rectangle with a width equal to the radius and an equal area. The perimeter of the rectangle is 20.7 cm. What is the area of the circle in square centimeters?
把一个圆分成若干个扇形剪开拼成一个宽等于半径，面积相等的长方形，这个长方形的周长是20.7厘米，圆的面积是多少平方厘米．
<gadget id="calculator">20.7 / 8.28</gadget>
<output>2.5</output>

<gadget id="calculator">3.14 * 2.5 * 2.5</gadget>
<output>19.625</output>

<result>19.625</result>