How many square decimeters of iron sheets are needed to make a chimney with a base diameter of 20 centimeters and a length of 1 meter with 10 sections.
做10节底面直径20厘米，长1米的烟囱，至少需要多少平方分米的铁皮．
<gadget id="calculator">20 / 10</gadget>
<output>2</output>

<gadget id="calculator">3.14 * 2 * 1 * 10 * 1 * 10</gadget>
<output>628</output>

<result>628</result>