The fuel carried by a ship can be used for up to 12 hours. When it sails out, it travels 30 kilometers per hour along the current. When it returns, it travels against the current. The ship should return as far as it sails.
一艘轮船所带的燃料最多可用12小时，驶出时顺水，每小时行驶30千米，返回时逆水，每小时行的路程是顺水时的(4/5)．这艘轮船最多驶出多远就应返回．
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">30 * (4/5)</gadget>
<output>24</output>

<gadget id="calculator">1 / 24</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">(1/30) + (1/24)</gadget>
<output>3/40 = around 0.075</output>

<gadget id="calculator">12 / (3/40)</gadget>
<output>160</output>

<result>160</result>