To make a cylindrical ventilation pipe with a length of 50 centimeters and a diameter of 20 centimeters at the bottom, how many square centimeters of iron sheets are needed at least? ．
制作一节圆柱形通风管，长50厘米，底面直径是20厘米，至少需要铁皮多少平方厘米？．
<gadget id="calculator">3.14 * 20 * 50</gadget>
<output>3_140</output>

<result>3_140</result>