To make a cylindrical ventilation pipe with a base diameter of 30 cm and a length of 60 cm, at least how many square centimeters of iron sheet should be used?
制作一个底面直径为30厘米，长60厘米的圆柱形通风管，至少要用多少平方厘米的铁皮？
<gadget id="calculator">3.14 * 30 * 60</gadget>
<output>5_652</output>

<result>5_652</result>