Obviously travel 6 kilometers per hour from point A to point B, and travel 4 kilometers per hour from point B to point A along the original road. What is the average speed of the round trip in kilometers?
明明从A地到B地每小时行6千米，从B地沿原路返回A地每小时行4千米，明明往返的平均速度是多少千米．
<gadget id="calculator">1 * 2</gadget>
<output>2</output>

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

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

<gadget id="calculator">(1/6) + (1/4)</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>