The scale of a map is 1:400000, and 4 cm on the map represents the actual distance in kilometers.
一幅地图的比例尺为1：400000，图上4厘米表示实际距离多少千米．
<gadget id="calculator">1 / 400_000</gadget>
<output>1/400_000 = around 0.000002</output>

<gadget id="calculator">4 / (1/400_000) / 100_000</gadget>
<output>16</output>

<result>16</result>