The distance between A and B is 720 kilometers. Two trains depart from the two places at the same time. After 4.5 hours, they meet. The distance between A and B is 72 kilometers per hour. How many kilometers per hour does B travel?
甲、乙两地相距720千米，两列火车同时从两地相对开出，经过4.5小时相遇，甲车每小时72千米，乙车每小时行多少千米？
<result>72</result>