On a map with a scale of 1:2000000, A. The distance between B and B is 4.5cm. If a truck departs from A at 10 am and arrives at B at 11:30, how many kilometers per hour does the truck travel on average?
在比例尺是1：2000000的地图上，量得A．B两地相距4.5cm，如果一辆货车上午10点从A地出发，11：30到达B地，那么货车平均每小时行驶多少千米？
<gadget id="calculator">1 / 2_000_000</gadget>
<output>1/2_000_000 = around 0</output>

<gadget id="calculator">11.5 - 10</gadget>
<output>1.5</output>

<gadget id="calculator">4.5 / (1/2_000_000) / 100_000 / 1.5</gadget>
<output>60</output>

<result>60</result>