ship sails 420 kilometers along the current and 80 kilometers against the current for the first time, and it takes 11 hours; it takes the same time to sail 240 kilometers along the current and 140 kilometers against the current for the second time. How many hours does it take for the ship to sail 198 km down the river?
一艘船，第一次顺水航行420千米，逆水航行80千米，用11小时；第二次用同样的时间顺水航行240千米，逆水航行140千米．这艘船顺水行198千米需要多少小时．
<gadget id="calculator">420 - 240</gadget>
<output>180</output>

<gadget id="calculator">140 - 80</gadget>
<output>60</output>

<gadget id="calculator">180 / 60</gadget>
<output>3</output>

<gadget id="calculator">80 * 3</gadget>
<output>240</output>

<gadget id="calculator">420 + 240</gadget>
<output>660</output>

<gadget id="calculator">660 / 11</gadget>
<output>60</output>

<gadget id="calculator">198 / 60</gadget>
<output>33/10 = around 3.3</output>

<result>33/10 = around 3.3</result>