The radius of the front wheel of a road roller is 0.5 meters, what is the circumference of the front wheel in meters?
一台压路机前轮半径是0.5米，前轮周长是多少米？
<gadget id="calculator">3.14 * 0.5 * 2</gadget>
<output>3.14</output>

<result>3.14</result>