Use a 20-meter-long rope to go around a column in the hall 6 times, and there is still 1.16 meters left. What is the cross-sectional area of this cylinder.
用一根长20米的绳子围绕大厅的一个圆柱绕了6圈还余下1.16米．这个圆柱的横截面面积是多少．
<gadget id="calculator">20 - 1.16</gadget>
<output>18.84</output>

<gadget id="calculator">18.84 / 6 / 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>