Xiao Ming is sitting on the moving train, and it takes 6 seconds to see the oncoming truck passing by from the window. It is known that the truck is 168 meters long; later, it takes 12 seconds to see the train passing a 180-meter-long bridge from the window. How many miles does the truck travel per hour?
小明坐在行驶的列车上，从窗外看到迎面开来的货车经过用了6秒，已知货车长168米；后来又从窗外看到列车通过一座180米长的桥用了12秒．货车每小时行多少千米．
<result>46.8</result>