To make a chimney with a bottom diameter of 2 decimeters and a length of 1 meter, at least how many square decimeters of iron sheets are needed.
做一节底面直径为2分米，长1米的烟囱，至少需要多少平方分米的铁皮．
<gadget id="calculator">3.14 * 2 * 1 * 10</gadget>
<output>62.8</output>

<result>62.8</result>