Divide a circle into several parts on average, and cut them to form an approximate rectangle. The perimeter of this rectangle is 16.56 decimeters. What is the area of this circle in square decimeters?
把一个圆的平均分成若干份，剪开后可以拼成一个近似的长方形，这个长方形的周长是16.56分米，这个圆的面积是多少平方分米．
<gadget id="calculator">3.14 * 2</gadget>
<output>6.28</output>

<gadget id="calculator">6.28 + 2</gadget>
<output>8.28</output>

<gadget id="calculator">16.56 / 8.28</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>