A ship sails from port A to port B, travels 30 kilometers per hour, arrives in 2.4 hours, and takes 3.6 hours to return. How many kilometers per hour does the ship travel when returning?
一艘轮船从甲港驶向乙港，每小时行30千米，2.4小时到达，返回时用了3.6小时，该轮船返回时每小时行多少千米？
<gadget id="calculator">2.4 / 3.6</gadget>
<output>0.666667</output>

<gadget id="calculator">30 * 0.666667</gadget>
<output>20.00001</output>

<result>20.00001</result>