The surface area of a circular ventilation pipe with a length of 2 meters is 62.8 square decimeters, what is the diameter of its bottom surface?
一个长2米的圆形通风管的表面积是62.8平方分米，那么它的底面直径是多少．
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">62.8 / 20 / 3.14</gadget>
<output>1</output>

<result>1</result>