At least how many square decimeters of iron sheet are needed to make a cylindrical iron sheet ventilation pipe with a bottom diameter of 2 decimeters and a height of 1 meter (not counting the joints).
做一个底面直径2分米，高1米的圆柱形铁皮通风管(接头处不计)至少要多少平方分米铁皮．
<gadget id="calculator">3.14 * 2 * 1 * 10</gadget>
<output>62.8</output>

<result>62.8</result>