On a map with a scale of (1/500000), the distance between A and B is 4 cm. What is the actual distance between A and B in kilometers?
在比例尺是(1/500000)的地图上量得甲、乙两地的距离是4厘米，甲、乙两地的实际距离是多少千米．
<gadget id="calculator">1 / 500_000</gadget>
<output>1/500_000 = around 0.000002</output>

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

<result>20</result>