A kind of ventilation pipe, the diameter of the bottom surface is 10 cm, and the length is 1.2 meters. To make 50 such ventilation pipes, at least how many square meters of iron sheets are needed? (neglected at the interface)
一种通风管，底面直径是10厘米，长1.2米，做50根这样的通风管，至少需要铁皮多少平方米？(接口处忽略不计)
<gadget id="calculator">50 / 10_000</gadget>
<output>1/200 = around 0.005</output>

<gadget id="calculator">3.14 * 10 * 1.2 * 100 * (1/200)</gadget>
<output>18.84</output>

<result>18.84</result>