The ship travels between the two terminals at the same speed. It went downstream for 8 hours and upstream for 10 hours. If the velocity of the water is 3 km/h, find the distance between the two piers.
轮船以同一速度往返于两码头之间．它顺流而下，行了8小时；逆流而上，行了10小时．如果水流速度是3千米/小时，求两码头之间的距离．
<gadget id="calculator">3 + 3</gadget>
<output>6</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/8) - (1/10)</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">6 / (1/40)</gadget>
<output>240</output>

<result>240</result>