The speed of the boat in still water is 25 kilometers per hour, and the speed of the current is 5 kilometers. It takes 9 hours for a boat to go back and forth between the two ports. How many kilometers is the distance between the two ports?
船在静水中的速度是每小时25千米，水流速度是5千米，一只船往返于两港之间共花了9小时，两港相距多少千米．
<gadget id="calculator">9 * 25 * 25</gadget>
<output>5_625</output>

<gadget id="calculator">9 * 5 * 25</gadget>
<output>1_125</output>

<gadget id="calculator">9 * 25 * 5</gadget>
<output>1_125</output>

<gadget id="calculator">9 * 5 * 5</gadget>
<output>225</output>

<gadget id="calculator">1_125 - 1_125 - 225</gadget>
<output>-225</output>

<gadget id="calculator">5_625 + (-225)</gadget>
<output>5_400</output>

<gadget id="calculator">5 - 5</gadget>
<output>0</output>

<gadget id="calculator">25 + 25 + 0</gadget>
<output>50</output>

<gadget id="calculator">5_400 / 50</gadget>
<output>108</output>

<result>108</result>