The front wheel of a road roller is cylindrical and has a diameter of 1 meter. How many meters does the roller advance when the front wheel rotates once?
一台压路机的前轮是圆柱形，直径1米．前轮转动一周，压路机前进多少米．
<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

<result>3.14</result>