On a map with a scale of 1:3000000, the measured distance between the two places is 4.2 cm. What is the actual distance in kilometers between the two places?
在一幅比例尺是1：3000000的地图上，量得两地距离是4.2厘米，两地的实际距离是多少千米．
<gadget id="calculator">1 / 3_000_000</gadget>
<output>1/3_000_000 = around 0</output>

<gadget id="calculator">4.2 / (1/3_000_000) / 100_000</gadget>
<output>126</output>

<result>126</result>