The scale of a map is 1:500000, how much is the actual 20 kilometers drawn on the map.
一副地图的比例尺是1：500000，实际的20千米画在图上有多少．
<gadget id="calculator">1 / 500_000</gadget>
<output>1/500_000 = around 0.000002</output>

<gadget id="calculator">20 * 1_000 * (1/500_000) * 100</gadget>
<output>4</output>

<result>4</result>