On a map with a scale of 1:4500000, the distance between A and B is measured to be 20 cm. How many kilometers is the actual distance between A and B?
在一幅比例尺是1：4500000的地图上，量得甲乙两地之间的距离是20厘米，甲乙两地的实际距离是多少千米？
<gadget id="calculator">1 / 4_500_000</gadget>
<output>1/4_500_000 = around 0</output>

<gadget id="calculator">20 / (1/4_500_000) / 100_000</gadget>
<output>900</output>

<result>900</result>