Wang Qiang went to the park on foot, and took a car when he came back. It took 1.5 hours to go back and forth. If he walks back and forth, it takes 2.5 hours. Then, how many minutes does it take him to go back and forth by car?
王强步行去公园，回来时坐车，往、返用了1.5小时．如果他来回都步行，则需要2.5小时，那么，他往、返都坐车，则需多少分钟．
<result>30</result>