The fuel carried by an aircraft can be used for up to 9 hours. When the aircraft goes with the wind, it can fly 2,500 kilometers per hour, and when it flies back against the wind, it can fly 2,000 kilometers per hour. Fly back?
一架飞机所带的燃料最多可以用9小时，飞机去时顺风，每小时飞行2500千米，飞回时逆风，每小时飞行2000千米，这架飞机最多飞出多少千米，就需往回飞？
<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">9 * (4/9)</gadget>
<output>4</output>

<gadget id="calculator">2_500 * 4</gadget>
<output>10_000</output>

<result>10_000</result>