Two boats, A and B, are sailing towards each other at two docks on the same river at the same time, and boat A is going in the opposite direction. After 9 hours, ship B meets A at a point 45 kilometers across the midpoint of the whole water journey. If both boats have the same speed in still water, what is the speed of the water?
甲、乙两船在同-条河流的两个码头同时相向而行，其中甲船逆行．经9小时乙船在越过全水程中点45千米处和甲相遇．如果两船的静水速度相同，问水流速度是多少？
<gadget id="calculator">2 / 9 / 2</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">45 * (1/9)</gadget>
<output>5</output>

<result>5</result>