A plane flies 600 kilometers per hour with a tailwind and arrives at its destination in 4 hours. Headwind when returning along the original route, arrived 6 hours later. Find the average round-trip speed of the plane.
一架飞机顺风时每小时飞行600千米，4小时后到达目的地．沿原航线返回时逆风，6小时后到达．求这架飞机往返的平均速度．
<gadget id="calculator">600 * 4 * 2</gadget>
<output>4_800</output>

<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<gadget id="calculator">4_800 / 10</gadget>
<output>480</output>

<result>480</result>