The fuel carried by an aircraft can be used for up to 18 hours. The aircraft can fly 1600km per hour with a downwind, and 1280km per hour with a headwind when returning. How many kilometers can this aircraft fly at most?
一架飞机所带的燃料最多可以用18小时，飞机去时顺风每小时可飞行1600km，返回时逆风，每小时可飞行1280km，这架飞机最多能飞出多少千米？
<gadget id="calculator">1 / 1_600</gadget>
<output>1/1_600 = around 0.000625</output>

<gadget id="calculator">1 / 1_280</gadget>
<output>1/1_280 = around 0.000781</output>

<gadget id="calculator">(1/1_600) + (1/1_280)</gadget>
<output>9/6_400 = around 0.001406</output>

<gadget id="calculator">18 / (9/6_400)</gadget>
<output>12_800</output>

<result>12_800</result>