On a map with a scale of 1:200000, the distance between A and B is 20 cm. What is the actual distance in miles between A and B?
在一幅比例尺是1：200000的地图上，量得A地和B地的图上距离为20厘米．则A、B两地的实际距离是多少千米．
<gadget id="calculator">20 / 100_000</gadget>
<output>1/5_000 = around 0.0002</output>

<gadget id="calculator">200_000 * (1/5_000)</gadget>
<output>40</output>

<result>40</result>