A ventilation pipe has a bottom diameter of 100 centimeters and a length of 1 meter. To make 100 such ventilation pipes, how many square decimeters of iron sheet are needed at least?
一种通风管的底面直径是100厘米，长1米，做100根这样的通风管，至少需要铁皮多少平方分米？
<gadget id="calculator">100 / 10</gadget>
<output>10</output>

<gadget id="calculator">3.14 * 1 * 10 * 1 * 10 * 100</gadget>
<output>31_400</output>

<result>31_400</result>