The radius of the front wheels of a road roller is 0.5 meters, and the length is 1.5 meters. What is the length of the ground that the roller rolls forward for 30 revolutions?
一台压路机的前轮半径为0.5米，长度为1.5米，向前滚动30周所压过地面的长度为多少？
<gadget id="calculator">2 * 3.14 * 0.5 * 1.5</gadget>
<output>4.71</output>

<gadget id="calculator">4.71 * 30</gadget>
<output>141.3</output>

<result>141.3</result>