A boat travels between ports A and B. From A to B, it travels along the current; from B to A, it travels against the current. It is known that the speed of the ship in still water is 8 kilometers per hour. The time it usually takes to go retrograde and to go forward The ratio is 2:1. One day it happened to be raining heavily. The speed of the water flow is doubled, and it takes 9 hours for the boat to go back and forth. How many kilometers are there between the two ports of A and B?
一条船往返于甲、乙两港之间，由甲至乙是顺水行驶；由乙至甲是逆水行驶，已知船在静水中的速度为每小时8公里，平时逆行与顺行所用时间的比为2：1．某天恰逢暴雨．水流速度变为原来的2倍，这条船往返共用9小时，那么甲乙两港相距多少公里？
<gadget id="calculator">40 / 18</gadget>
<output>20/9 = around 2.222222</output>

<gadget id="calculator">9 * (20/9)</gadget>
<output>20</output>

<result>20</result>