On a map with a scale of (1/3000000), the length of the road between A and B is measured to be 12 cm. A car travels from A to B for 4.5 hours. What is the average speed of the car per hour? km?
在比例尺是(1/3000000)的地图上，量得甲、乙两地间的公路长12厘米，一辆汽车从甲地开往乙地，行了4.5小时，这辆汽车平均每小时行多少千米？
<gadget id="calculator">1 / 3_000_000</gadget>
<output>1/3_000_000 = around 0</output>

<gadget id="calculator">12 / (1/3_000_000) / 100_000 / 4.5</gadget>
<output>80</output>

<result>80</result>