It took Xiao Huang 4 hours to go up the mountain at 3 kilometers per hour; he went down the mountain by the original road and traveled 6 kilometers per hour. What is his average speed up and down the mountain in kilometers per hour
小黄上山每小时行3千米，用了4小时；有按原来的路下山，每小时行6千米．他上下山的平均速度是多少千米/小时
<gadget id="calculator">3 * 4 * 2</gadget>
<output>24</output>

<gadget id="calculator">4 / 6</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">3 * (2/3)</gadget>
<output>2</output>

<gadget id="calculator">4 + 2</gadget>
<output>6</output>

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

<result>4</result>