A plane can fly for up to 6 hours with fuel. When flying out, it can fly 900 kilometers per hour with a tailwind. When returning, the headwind speed is reduced by 20%. How many kilometers should this plane fly before returning?
一架飞机所带燃油最多可飞行6小时，飞出去时顺风每小时飞行900千米，返回时逆风速度降低了20%，这架飞机最多飞出多少千米就应返回？
<gadget id="calculator">6 * 900</gadget>
<output>5_400</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">6 * 900 * (1/5)</gadget>
<output>1_080</output>

<gadget id="calculator">5_400 - 1_080</gadget>
<output>4_320</output>

<gadget id="calculator">900 * (1/5)</gadget>
<output>180</output>

<gadget id="calculator">900 - 180</gadget>
<output>720</output>

<gadget id="calculator">900 + 720</gadget>
<output>1_620</output>

<gadget id="calculator">4_320 / 1_620</gadget>
<output>8/3 = around 2.666667</output>

<gadget id="calculator">900 * (8/3)</gadget>
<output>2_400</output>

<result>2_400</result>