A boat travels between ports A and B. It is known that the speed of the boat in still water is 9 km/h, and the ratio of the time it takes to go retrograde to forward is 2:1. One day, due to rain, the speed of the water flow is doubled. The boat takes 10 hours to go back and forth. How many kilometers is the distance between A and B?
一条船往返于甲、乙两港之间，已知船在静水中的速度为9千米/小时，平时逆行与顺行所用时间的比为2：1．一天因下雨，水流速度为原来的2倍，这条船往返共用10小时，问甲、乙两港相距多少千米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * 9</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">9 - (9/2)</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">1 + (1/2)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">(9/2) / (3/2)</gadget>
<output>3</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">9 + 6</gadget>
<output>15</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">15 * 10 * (1/6)</gadget>
<output>25</output>

<result>25</result>