On a map with a scale of 1:50000, the actual distance is 20 kilometers, what is the distance on the map?
在一副比例尺是1：50000的地图上，实际距离是20千米，图上距离是多少．
<gadget id="calculator">1 / 50_000</gadget>
<output>1/50_000 = around 0.00002</output>

<gadget id="calculator">20 * 100_000 * (1/50_000)</gadget>
<output>40</output>

<result>40</result>