The length of the railway between cities A and B is 612 kilometers. A train of passenger cars and a train of freight trains depart from the two places at the same time and meet each other in 4.5 hours. The passenger train travels 72 kilometers per hour. How many kilometers per hour does the freight train travel?
甲、乙两城市的铁路长612千米，一列客车和一列货车分别从两地同时相对开出，4.5小时相遇，客车每小时行72千米，货车每小时行多少千米？
<gadget id="calculator">612 / 4.5</gadget>
<output>136</output>

<gadget id="calculator">136 - 72</gadget>
<output>64</output>

<result>64</result>