On a map with a scale of 1:4000000, the distance between Yimen and Kunming is measured as 2.25 cm. What is the actual distance between Yimen and Kunming in kilometers?
在比例尺为1：4000000的地图上，量得易门到昆明的距离为2.25厘米，易门到昆明的实际距离是多少千米．
<gadget id="calculator">1 / 4_000_000</gadget>
<output>1/4_000_000 = around 0</output>

<gadget id="calculator">2.25 / (1/4_000_000) / 100_000</gadget>
<output>90</output>

<result>90</result>