On a map, the actual distance of 900 km is represented by a line segment 3 cm long. On this map, the actual distance between A and B is 2.5 cm. What is the actual distance between A and B in kilometers?
在一幅地图上，用3厘米长的线段表示实际距离900千米．在这幅地图上量得A、B两地的实距离是2.5厘米，A、B两地的实际距离是多少千米．
<gadget id="calculator">900 * 100_000</gadget>
<output>90_000_000</output>

<gadget id="calculator">3 / 90_000_000</gadget>
<output>1/30_000_000 = around 0</output>

<gadget id="calculator">2.5 / (1/30_000_000) / 100_000</gadget>
<output>750</output>

<result>750</result>