A freight train and a passenger train depart from two stations A and B which are 480 kilometers apart at the same time. The freight train travels 54 kilometers per hour, and the passenger train travels 66 kilometers per hour. How many hours after the two trains drive, they meet.
一列货车和一列客车分别从相距480千米的甲、乙两站同时相对开出，货车每小时行54千米，客车每小时行66千米，两车开出多少小时后相遇．
<gadget id="calculator">54 + 66</gadget>
<output>120</output>

<gadget id="calculator">480 / 120</gadget>
<output>4</output>

<result>4</result>