A train takes 20 hours from station A to station B and travels 120 kilometers per hour. It took 30 hours to return, how many kilometers per hour when returning?
一列火车从甲站到乙站一共用了20时，每小时行120千米．返回时用了30小时，返回时每小时行多少千米？
<gadget id="calculator">120 / 30</gadget>
<output>4</output>

<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>