An express train and a slow train depart from two places 630 kilometers apart at the same time and meet each other in 4.5 hours. The express train travels 78 kilometers per hour. How many kilometers per hour does the slow train travel?
一列快车和一列慢车同时分别从相距630千米的两地相对开出，4.5小时相遇，快车每小时行78千米，慢车每小时行多少千米？
<gadget id="calculator">630 / 4.5</gadget>
<output>140</output>

<gadget id="calculator">140 - 78</gadget>
<output>62</output>

<result>62</result>