Find the actual distance: On a map with a scale of 1:30000000, the distance between Beijing and Changsha is measured to be 5.1 cm. How many kilometers is the actual distance between Beijing and Changsha?
求实际距离：在比例尺是1：30000000的地图上，量得北京到长沙的距离是5.1厘米，问北京到长沙的实际距离是多少千米？
<gadget id="calculator">1 / 30_000_000</gadget>
<output>1/30_000_000 = around 0</output>

<gadget id="calculator">5.1 / (1/30_000_000) / 100_000</gadget>
<output>1_530</output>

<result>1_530</result>