road roller, with a front wheel diameter of one meter and a wheel width of 1.2 meters, turns 3 revolutions per minute, how much does it pass over the road after working for half an hour?
一台压路机，前轮直径一米，轮宽1.2米，每分转动3圈，工作半小时压过路面是多少？
<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

<gadget id="calculator">3.14 * 1.2 * 3 * 30</gadget>
<output>339.12</output>

<result>339.12</result>