A square and a circle have the same perimeter. The side length of the square is 4.71 decimeters. Find the area of the circle.
一个正方形和一个圆的周长相等．正方形的边长是4.71分米．求圆的面积．
<gadget id="calculator">4.71 * 4</gadget>
<output>18.84</output>

<gadget id="calculator">18.84 / 3.14 / 2</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>