The fuel that a plane can carry can be used for up to 6 hours, and the plane goes with the wind. It can fly 1500KM per hour, and when flying back against the wind, it can fly 1200KM per hour. Ask how many kilometers this plane can fly at most, and then it needs to fly back?
一架飞机能带的燃料最多可以用6小时，飞机去时顺风．每小时可以飞1500KM，飞回时逆风，每小时可以飞1200KM．问这架飞机最多能飞多少KM，就需往回飞？
<gadget id="calculator">1 / 1_500</gadget>
<output>1/1_500 = around 0.000667</output>

<gadget id="calculator">1 / 1_200</gadget>
<output>1/1_200 = around 0.000833</output>

<gadget id="calculator">(1/1_500) + (1/1_200)</gadget>
<output>3/2_000 = around 0.0015</output>

<gadget id="calculator">6 / (3/2_000)</gadget>
<output>4_000</output>

<result>4_000</result>