Wang Qiang went to the park on foot, and took a car when he came back. It took him one and a half hours to go back and forth. If he walked all the way back and forth, it would take two and a half hours.
王强步行去公园，回来时坐车，往返用了一个半小时，如果他来回都步行，则需要2个半小时，那么，他来会都坐车，则需多少分钟．
<result>30</result>