On a map, the actual distance of 20 km is represented by a line segment of 1 cm long. What is the scale of the map?
在一幅地图上用1cm长的线段表示20km的实际距离，这地图的比例尺是多少
<gadget id="calculator">1 / 2_000_000</gadget>
<output>1/2_000_000 = around 0</output>

<result>1/2_000_000 = around 0</result>