The railway from Changsha to Guangzhou is 728km long, and a freight train travels 71km per hour from Guangzhou to Changsha. A passenger train departs from Changsha to Guangzhou at the same time, and the two trains meet after 4 hours. What is the speed of this passenger train?
长沙到广州的铁路长728km，一列货车从广州开往长沙，每小时行71km．一列客车从长沙同时开往广州，4小时后两车相遇，这列客车的速度是多少？
<gadget id="calculator">728 / 4</gadget>
<output>182</output>

<gadget id="calculator">182 - 71</gadget>
<output>111</output>

<result>111</result>