The fuel carried by a ship can be used for up to 27 hours. When the ship goes along the river, it can travel 15 kilometers per hour, and when it returns, it can travel 12 kilometers per hour against the current. How far is the ship’s distance? Driving back?
一艘轮船所带的燃料最多可以用27小时，轮船去时顺水而行，每小时可以行15千米，回时逆水每小时可以行12千米，问这艘船最远行驶多少千米就要往回行驶？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/15) + (1/12)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">27 / (3/20)</gadget>
<output>180</output>

<result>180</result>