A map, 20 centimeters on the map means the actual distance is 100 kilometers, what is the scale of this map
一副地图，图上的20厘米表示实际距离100千米，这幅地图的比例尺是多少
<gadget id="calculator">100 * 100_000</gadget>
<output>10_000_000</output>

<gadget id="calculator">20 / 10_000_000</gadget>
<output>1/500_000 = around 0.000002</output>

<result>1/500_000 = around 0.000002</result>