train passes a certain mountain. It travels 30.5 kilometers per hour when going up the mountain, and 50.8 kilometers per hour when going down the mountain. It is known that it takes 6 hours to go up the mountain and 4 hours to go down the mountain. Find the average speed of the train going up and down the mountain?
一列火车经过某山，上山时每小时行30.5千米，下山时每小时行50.8千米，已知上山用了6小时，下山用了4小时，求这列车上、下山的平均速度？
<gadget id="calculator">30.5 * 6</gadget>
<output>183</output>

<gadget id="calculator">50.8 * 4</gadget>
<output>203.2</output>

<gadget id="calculator">183 + 203.2</gadget>
<output>386.2</output>

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

<gadget id="calculator">386.2 / 10</gadget>
<output>38.62</output>

<result>38.62</result>