On a map with a scale of (1/5000000), the length of the railway between A and B is measured to be 8.4 cm. What is the actual distance in kilometers between A and B by railway?
在比例尺是(1/5000000)的地图上，量得甲乙两地的铁路长8.4厘米．甲乙两地的铁路实际距离是多少千米．
<gadget id="calculator">1 / 5_000_000</gadget>
<output>1/5_000_000 = around 0</output>

<gadget id="calculator">8.4 / (1/5_000_000) / 100_000</gadget>
<output>420</output>

<result>420</result>