The radius of the driving wheel of the train is 75 centimeters. If it rotates 300 times per minute on average, how many kilometers does the train travel per hour?
火车主动轮的半径为75厘米，如果平均每分钟转300周，这列火车每小时行多少千米？
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<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">2 * 3.14 * (3/4) * 300 * 1 * (3/50)</gadget>
<output>84.78</output>

<result>84.78</result>