A ship sails from port A to port B, sails 40 kilometers per hour, arrives in 12 hours, and sails 30 kilometers per hour when returning, how many hours will it arrive? (Answer with proportional knowledge)
一艘轮船从甲港开往乙港，每小时航行40千米，12小时到达，返回时每小时航行30千米，几小时到达？(用比例知识解答)
<gadget id="calculator">40 * 12</gadget>
<output>480</output>

<gadget id="calculator">480 / 30</gadget>
<output>16</output>

<result>16</result>