The diameter of the driving wheel of a train locomotive is 2 meters. When the train is running, the drive wheel rotates an average of 300 times per minute. Approximately how many kilometers per hour does the train travel?
一列火车的机车主动轮的直径是2米．火车运行时，主动轮平均每分转300圈．这列火车每小时大约行驶多少千米？
<gadget id="calculator">1 * 1_000</gadget>
<output>1_000</output>

<gadget id="calculator">60 / 1_000</gadget>
<output>3/50 = around 0.06</output>

<gadget id="calculator">3.14 * 2 * 300 * 1 * (3/50)</gadget>
<output>113.04</output>

<result>113.04</result>