To make a chimney with a bottom diameter of 2 decimeters and a length of 8.5 decimeters, at least how many square decimeters of iron sheet is needed.
做一个底面直径为2分米，长8.5分米的烟筒，至少需要多少平方分米的铁皮．
<gadget id="calculator">3.14 * 2 * 8.5</gadget>
<output>53.38</output>

<result>53.38</result>