The length of a rope that wraps exactly three times around the trunk of a big tree is 37.68dm. What is the cross-sectional area of the big tree?
一根绳子，正好绕一棵大树的树干3圈的长是37.68dm，这棵大树的横截面的面积是多少？
<gadget id="calculator">37.68 / 3 / 3.14 / 2</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>