On a map of China with a scale of 1:25000000, the distance between Beijing and Shanghai is measured to be 4.2 centimeters, so how many kilometers should the actual distance be from Beijing to Shanghai?
在比例尺是1：25000000的中国地图上，量得北京到上海的距离是4.2厘米，则北京到上海的实际距离应是多少千米．
<gadget id="calculator">1 / 25_000_000</gadget>
<output>1/25_000_000 = around 0</output>

<gadget id="calculator">4.2 / (1/25_000_000) / 100_000</gadget>
<output>1_050</output>

<result>1_050</result>