A ventilation pipe has a bottom diameter of 10 cm and a length of 1 meter. Make 100 such ventilation pipes. How many square meters of iron sheet is needed at least?
一种通风管的底面直径是10厘米，长1米，做100根这样的通风管．至少需要铁皮多少平方米？
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">3.14 * (1/10) * 1 * 100</gadget>
<output>31.4</output>

<result>31.4</result>