It is 24 kilometers from the foot of the mountain to the top of the mountain. A person goes up the mountain at a speed of 4 kilometers per hour. He immediately goes down the mountain from the same road. It is known that the speed of going down the mountain is 6 kilometers. What is the average speed of his going up and down the mountain in kilometers?
山脚到山顶有24千米．一个人以每小时4千米的速度上山，他立即从原路下山，已知下山的速度是6千米，他上山和下山的平均速度是多少千米？
<gadget id="calculator">24 + 24</gadget>
<output>48</output>

<gadget id="calculator">24 / 4</gadget>
<output>6</output>

<gadget id="calculator">24 / 6</gadget>
<output>4</output>

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

<gadget id="calculator">48 / 10</gadget>
<output>24/5 = around 4.8</output>

<result>24/5 = around 4.8</result>