On a map marked with a scale of 1:4000000, the distance between cities A and B is measured to be 15 cm. What is the actual distance between cities A and B in kilometers?
在一幅标有1：4000000的比例尺的地图上量得甲乙两城市之间的距离是15厘米，甲乙两城市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">15 / (1/4_000_000) / 100_000</gadget>
<output>600</output>

<result>600</result>