When a train travels from A to B and returns, its speed increases (1/5), and it arrives at A 1 hour earlier. The distance between A and B is 440 kilometers. Find the average round-trip speed of this train.
一列火车从甲地开往乙地返回时，速度提高(1/5)，结果提前1小时到达甲地．甲、乙两地相距440千米，求这列火车的往返平均速度．
<gadget id="calculator">6 - 5</gadget>
<output>1</output>

<gadget id="calculator">1 / 1</gadget>
<output>1</output>

<gadget id="calculator">1 * 6</gadget>
<output>6</output>

<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">6 + 5</gadget>
<output>11</output>

<gadget id="calculator">2 / 11</gadget>
<output>2/11 = around 0.181818</output>

<gadget id="calculator">440 * (2/11)</gadget>
<output>80</output>

<result>80</result>