To make a cylindrical chimney pipe with a length of 1 meter and a bottom radius of 10 cm, at least how many square meters of iron sheet is needed.
做一个长1米，底面半径为10厘米的圆柱形烟囱管，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">2 * 3.14 * (1/10) * 1</gadget>
<output>0.628</output>

<result>0.628</result>