A plane flies from A to B with a tailwind of 1,500 kilometers per hour. When returning to headwind, it can only fly 1,200 kilometers per hour. The round trip takes 6 hours. How many kilometers is the distance between A and B?
一架飞机从甲地飞往乙地，顺风每小时飞行1,500千米，返回时逆风，每小时只能飞行1,200千米，往返共用了6小时，甲、乙两地相距多少千米？
<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>