On a map with a scale of 1:20000000, the length of the road line between A and B is 4.5 cm. A passenger car and a truck depart from two places at the same time. After 6 hours, the two cars meet. The bus travels 90 kilometers per hour. How many kilometers per hour does the truck travel?
在比例尺是1：20000000的地图上，量得A、B两地的公路线长为4.5厘米．一辆客车与一辆货车分别同时从两地相对开出，6小时后两车相遇，客车每小时行90千米，货车每小时行多少千米？
<gadget id="calculator">1 / 20_000_000</gadget>
<output>1/20_000_000 = around 0</output>

<gadget id="calculator">4.5 / (1/20_000_000) / 100_000 / 6</gadget>
<output>150</output>

<gadget id="calculator">150 - 90</gadget>
<output>60</output>

<result>60</result>