The diameter of a circular garden is 20 meters, what is the area of the garden in square meters?
一个圆形花园的直径是20米，这个花园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">3.14 * 100</gadget>
<output>314</output>

<result>314</result>