The distance between the two piers is 200 kilometers. It takes 8 hours for a ship to travel downstream and 10 hours to travel upstream. What is the velocity of the water in this river in km/h?
两个码头相距200千米，一艘轮船顺流而下行完全程需8小时，逆流而上行完全程需10小时．则这条河的水流速度是多少千米/时．
<gadget id="calculator">200 / 8</gadget>
<output>25</output>

<gadget id="calculator">200 / 10</gadget>
<output>20</output>

<gadget id="calculator">25 - 20</gadget>
<output>5</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>