How many square meters of iron sheet is needed to make a cylindrical ventilation pipe with a bottom diameter of 2 decimeters and a length of 1.5 meters.
用铁皮做一个底面直径是2分米，长1.5米的圆柱形通风管，大约需要铁皮多少平方米．
<gadget id="calculator">2 / 10</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3.14 * (1/5) * 1.5</gadget>
<output>0.942</output>

<result>0.942</result>