On a map with a scale of 1:20000, the distance between A and B is 4 cm. What is the actual distance between A and B?
在一幅比例尺为1：20000的地图上，量得甲、乙两地间的距离为4厘米．甲、乙两地间的实际距离是多少米？
<gadget id="calculator">1 / 20_000</gadget>
<output>1/20_000 = around 0.00005</output>

<gadget id="calculator">4 / (1/20_000)</gadget>
<output>80_000</output>

<gadget id="calculator">80_000 / 100</gadget>
<output>800</output>

<result>800</result>