The radius of the wheel is 0.3 meters, how many meters does the wheel move on the ground in one revolution?
车轮的半径是0.3米，车轮在地面上滚动一周前进多少米．
<gadget id="calculator">2 * 3.14 * 0.3</gadget>
<output>1.884</output>

<result>1.884</result>