The roller of the roller is a cylinder. Its cross-sectional diameter is 1.6 meters and its length is 2 meters. How much road surface can it roll over once? If the roller advances 40 meters per minute, how big is the rolling area after half an hour?
压路机的滚筒是一个圆柱．它的横截面直径是1.6米，长是2米，它滚一周能压过多大的路面？如果压路机每分前进40米，半小时后压路面积有多大？
<gadget id="calculator">3.14 * 1.6 * 2</gadget>
<output>10.048</output>

<gadget id="calculator">10.048 * 40 * 30</gadget>
<output>12_057.6</output>

<result>12_057.6</result>