passenger ship sails at a speed of 26 km/h in still water, and travels between ports A and B, and the speed of the river is 6 km/h. If the passenger ship takes 13 hours to go back and forth 4 times in the river, then how many kilometers is the distance between A and B ports? (The turn-around time of passenger ships is not counted)
一艘客轮在静水中的航行速度是26千米/时，往返于A、B两港之间，河水的流速是6千米/时．如果客轮在河中往返4趟共用13小时，那么A、B两港之间相距多少千米．(客轮掉头时间不计)
<gadget id="calculator">13 / 4</gadget>
<output>13/4 = around 3.25</output>

<gadget id="calculator">5 + 8</gadget>
<output>13</output>

<gadget id="calculator">5 / 13</gadget>
<output>5/13 = around 0.384615</output>

<gadget id="calculator">(13/4) * (5/13)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">26 + 6</gadget>
<output>32</output>

<gadget id="calculator">(5/4) * 32</gadget>
<output>40</output>

<result>40</result>