small ship sails 130 kilometers downstream and 90 kilometers upstream, and it takes 12 hours. At this speed, it takes 8 hours to sail 105 kilometers downstream and 49 kilometers upstream. If there are two piers in a still water lake 30 kilometers apart, how many hours does it take for this small ship to make a round trip?
一艘小轮船顺流航行130千米，逆流航行90千米，需要12小时，按这样的速度顺流航行105千米，逆流航行49千米，需要8小时．如果一静水湖中有两个码头相距30千米，这艘小轮船往返一趟需要多少小时？
<gadget id="calculator">24 / 12</gadget>
<output>2</output>

<gadget id="calculator">24 / 8</gadget>
<output>3</output>

<gadget id="calculator">105 * 3</gadget>
<output>315</output>

<gadget id="calculator">130 * 2</gadget>
<output>260</output>

<gadget id="calculator">315 - 260</gadget>
<output>55</output>

<gadget id="calculator">90 * 2</gadget>
<output>180</output>

<gadget id="calculator">49 * 3</gadget>
<output>147</output>

<gadget id="calculator">180 - 147</gadget>
<output>33</output>

<gadget id="calculator">55 / 33</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">90 * (5/3)</gadget>
<output>150</output>

<gadget id="calculator">130 + 150</gadget>
<output>280</output>

<gadget id="calculator">280 / 12</gadget>
<output>70/3 = around 23.333333</output>

<gadget id="calculator">280 / 12 / (5/3)</gadget>
<output>14</output>

<gadget id="calculator">(70/3) + 14</gadget>
<output>112/3 = around 37.333333</output>

<gadget id="calculator">(112/3) / 2</gadget>
<output>56/3 = around 18.666667</output>

<gadget id="calculator">2 / (56/3)</gadget>
<output>3/28 = around 0.107143</output>

<gadget id="calculator">30 * (3/28)</gadget>
<output>45/14 = around 3.214286</output>

<result>45/14 = around 3.214286</result>