On a map with a scale of 1:4000000, the length of a section of railway is measured to be 30cm. What is the actual length of this railway in kilometers?
在比例尺是1：4000000的地图上，量得一段铁路的长是30cm．这段铁路的实际的长是多少千米？
<gadget id="calculator">1 / 4_000_000</gadget>
<output>1/4_000_000 = around 0</output>

<gadget id="calculator">30 / (1/4_000_000) / 100_000</gadget>
<output>1_200</output>

<result>1_200</result>