cylindrical chimney is 8 meters high and has a bottom diameter of 20 cm. How many square meters of iron sheet is needed to make such a chimney?
一个圆柱形烟囱高8米，底面直径20厘米，做一个这样的烟囱至少要多少平方米铁皮？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3.14 * (1/5) * 8</gadget>
<output>5.024</output>

<result>5.024</result>