On a map, the actual distance of 90 kilometers is represented by 2 centimeters. What is the scale of the map?
在一幅地图上，用2厘米表示实际距离90千米，这幅地图的比例尺是多少
<gadget id="calculator">90 * 100_000</gadget>
<output>9_000_000</output>

<gadget id="calculator">2 / 9_000_000</gadget>
<output>1/4_500_000 = around 0</output>

<result>1/4_500_000 = around 0</result>