On a map, the actual distance of 600 km is represented by a line segment of 3 cm. On this map, the distance between A and B is 4.5 cm. What is the actual distance between A and B in kilometers?
在一幅地图上，用3厘米的线段表示实际距离600千米．在这幅地图上，量得甲、乙两地的距离是4.5厘米，甲、乙两地的实际距离是多少千米？
<gadget id="calculator">600 * 100_000</gadget>
<output>60_000_000</output>

<gadget id="calculator">3 / 60_000_000</gadget>
<output>1/20_000_000 = around 0</output>

<gadget id="calculator">4.5 / (1/20_000_000) / 100_000</gadget>
<output>900</output>

<result>900</result>