Ports A and B are 288 kilometers apart. A ship travels 12 kilometers per hour along the current and 9 kilometers per hour against the current. How many hours does it take to go back and forth between the two ports?
甲、乙两个港口相距288千米，一艘轮船顺水每小时航行12千米，逆水每小时航行9千米．在两港来回一次共需要多少小时？
<gadget id="calculator">288 / 12</gadget>
<output>24</output>

<gadget id="calculator">288 / 9</gadget>
<output>32</output>

<gadget id="calculator">24 + 32</gadget>
<output>56</output>

<result>56</result>