Two trucks drive from two places 391.5 kilometers apart at the same time. Car A travels 40.5 kilometers per hour. After 4.5 hours, they meet each other. How many kilometers does car B travel per hour?
两辆货车分别从相距391.5千米的两地同时相对开出，甲车每小时行40.5千米，经过4.5小时相遇，问乙车每小时行多少千米？
<gadget id="calculator">391.5 / 4.5</gadget>
<output>87</output>

<gadget id="calculator">87 - 40.5</gadget>
<output>46.5</output>

<result>46.5</result>