To make two cylindrical ventilation pipes with a length of 120cm and a bottom diameter of 20cm, at least how many square centimeters of iron sheets are needed.
做两个长120cm，底面直径20cm的圆柱形通风管，至少需要铁皮多少平方厘米．
<gadget id="calculator">3.14 * 20 * 120 * 2</gadget>
<output>15_072</output>

<result>15_072</result>