A ship sails from port A to port B, travels 25 kilometers per hour, and arrives in 4.5 hours. It takes 5 hours to return from port B to port A. How many kilometers does it travel on average per hour when returning?
一艘轮船从甲港开往乙港，每小时行25千米，4.5小时到达，从乙港返回甲港时用了5小时，返回时平均每小时行多少千米？
<gadget id="calculator">4.5 / 5</gadget>
<output>0.9</output>

<gadget id="calculator">25 * 0.9</gadget>
<output>22.5</output>

<result>22.5</result>