The radius of a circle is 2 decimeters, what is its area in square decimeters
一个圆的半径是2分米，它的面积是多少平方分米
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

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

<result>12.56</result>