The line segment scale of a map is 1:4,000,000. The distance between A and B on this map is 18 cm. What is the actual distance in kilometers between the two cities?
一幅地图的线段比例尺是1：4000000，甲乙两城在这幅地图上相距18厘米，两城之间的实际距离是多少千米？
<gadget id="calculator">1 / 4_000_000</gadget>
<output>1/4_000_000 = around 0</output>

<gadget id="calculator">18 / (1/4_000_000) / 100_000</gadget>
<output>720</output>

<result>720</result>