A grove is surrounded by a circular path with an outer diameter of 20 meters and an inner radius of 9 meters. What is the area of the circular road in square meters?
一片小树林，周围有一条环形小路，外圆直径20米，内圆半径9米．环形的路的面积是多少平方米？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">9 ** 2</gadget>
<output>81</output>

<gadget id="calculator">100 - 81</gadget>
<output>19</output>

<gadget id="calculator">3.14 * 19</gadget>
<output>59.66</output>

<result>59.66</result>