How many square meters of steel plate should be used to install a ventilation pipe with a bottom diameter of 1 meter and a length of 5 meters?
安装一节底面直径为1米，长5米的通风管，至少用多少平方米的钢板．
<gadget id="calculator">3.14 * 1 * 5</gadget>
<output>15.7</output>

<result>15.7</result>