The fuel carried by an aircraft can be used for up to 6 hours. When the aircraft goes with a tailwind, the speed is 1500 kilometers per hour, and when it flies back against the wind, the wind speed is 150 kilometers per hour. So how many kilometers does the plane have to fly back?
一架飞机所带燃料最多可用6小时，飞机去时顺风，每小时1500公里，飞回时逆风，风速为每小时150公里，那么这架飞机最多飞出多少公里就得飞回？
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">1_500 * 6 * (4/9)</gadget>
<output>4_000</output>

<result>4_000</result>