How many square decimeters of iron sheet is required to make a cylindrical ventilation pipe with a length of 8 decimeters and a diameter of 1 decimeter at the bottom?
用铁皮制作1节圆柱形通风管，长是8分米，底面直径1分米，至少需要铁皮多少平方分米？
<gadget id="calculator">3.14 * 1 * 8</gadget>
<output>25.12</output>

<result>25.12</result>