On Sunday, Xiao Ming went to climb the mountain. He went up the mountain at 4km per hour, and went down the mountain along the original road at 6km per hour. Find the average speed of Xiaoming going up and down the mountain.
星期天，小明去爬山，上山每小时行4km，沿原路下山，每小时行6km，求小明上山和下山的平均速度．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/4) + (1/6)</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">2 / (5/12)</gadget>
<output>24/5 = around 4.8</output>

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