To make a cylindrical iron chimney with a length of 2 meters and a diameter of 20 cm, how many square meters of iron sheet is needed at least?
做一节长2米，直径20厘米的圆柱形铁皮烟囱，至少需要铁皮多少平方米？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3.14 * (1/5) * 2</gadget>
<output>1.256</output>

<result>1.256</result>