The distance between the two places is 280 kilometers, and a ship sails along the current from A to B. The speed of the boat in still water is 17 kilometers per hour, and the speed of the water is 3 kilometers per hour. How many hours does it take for the ship to go back and forth between A and B?
两地相距280千米，一艘轮船从甲地到乙地是顺水航行．船在静水中的速度是每小时行17千米，水速是每小时3千米．这艘轮船在甲、乙两地往返一次，共需多少小时．
<gadget id="calculator">17 + 3</gadget>
<output>20</output>

<gadget id="calculator">280 / 20</gadget>
<output>14</output>

<gadget id="calculator">17 - 3</gadget>
<output>14</output>

<gadget id="calculator">280 / 14</gadget>
<output>20</output>

<gadget id="calculator">14 + 20</gadget>
<output>34</output>

<result>34</result>