On a map with a scale of l:4000000, the distance between A and B on the map is 2.5cm. What is the actual distance between A and B in km?
在比例尺为l：4000000的地图上量得A、B两地的图上距离是2.5cm，A、B两地的实际距离是多少km．
<gadget id="calculator">1 / 4_000_000</gadget>
<output>1/4_000_000 = around 0</output>

<gadget id="calculator">2.5 / (1/4_000_000) / 100_000</gadget>
<output>100</output>

<result>100</result>