Make a ventilation pipe with iron sheet, its length is 80 cm, the diameter of the bottom surface is 10 cm, at least how many square centimeters of iron sheet is needed.
用铁皮制作一节通风管，它的长是80厘米，底面直径是10厘米，至少需要铁皮多少平方厘米．
<gadget id="calculator">3.14 * 10 * 80</gadget>
<output>2_512</output>

<result>2_512</result>