The fuel carried by a rescue helicopter can be used for up to 6 hours. The aircraft can fly 1,500 kilometers per hour with the wind; How many kilometers does this rescue helicopter have to fly back? (Solution of column equation)
一架救援直升机所带的燃料最多可以用6小时，飞机顺风，每小时飞行1500千米；返回时逆风，每小时可以飞1200千米．这架救援直升机最多飞出多少千米就要往回飞？(列方程解)
<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>