Wrap a 6.28-meter-long rope around the trunk of a big tree, and wrap it exactly twice. If this big tree is sawed at the place where the rope is wound, what is the cross-sectional area in square meters?
把一根长6.28米的绳子绕在一棵大树的树干上，正好绕了2圈．如果把这棵大树在绕绳子的地方锯开，横截面的面积是多少平方米？
<gadget id="calculator">6.28 / 2 / 3.14 / 2</gadget>
<output>0.5</output>

<gadget id="calculator">0.5 ** 2</gadget>
<output>0.25</output>

<gadget id="calculator">3.14 * 0.25</gadget>
<output>0.785</output>

<result>0.785</result>